ISSN 1000-3304CN 11-1857/O6
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Surface Modification of Ultra-high Molecular Weight Polyethylene Fiber by Catechol-tetraethylenepentamine
Han Zhao, Qing Shang, Meng Yang, Shuai Jin, Yang-yang Wang, Ning Zhao, Xiao-pin Yin, Cai-ling Ding, Jian Xu
六校 , doi: 10.11777/j.issn1000-3304.2019.19172
[Abstract](167) [FullText HTML](71) [PDF 1246KB](9)
In recent years, research on interface modification based on dopamine has been greatly developed, but the high price of dopamine limits its practical application. Cheap catechol-tetraethylenepentamine (Cat-TEPA), similar to dopamine, can spontaneously polymerize and then deposit on the surface of various materials, exhibiting strong adhesion, reactivity, and no selectivity to the substrate. Surface modification based on Cat-TEPA has become a universal method suitable for practical applications. In this paper, ultra-high molecular weight polyethylene (UHMWPE) fiber was modified by Cat-TEPA. Transmission electron microscopy (TEM), infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the static contact angle investigations were used to characterize the structure and performance of the modified fibers. The interfacial shear strength (IFSS) between the fiber and the epoxy resin before and after modification was measured by monofilament extraction experiment. The effects of reactant ratio and reaction time on interface properties were explored and the optimal modification conditions were determined. The results show that Cat-TEPA modification does not affect the crystallization and thermal stability of the fiber, and the surface wettability of the fiber is improved after modification. An optimal IFSS increase of about 44% has been obtained when the molar ratio of Cat-TEPA is 1:4 and reaction time is 24 h.
Synthesis of Carboxyl-terminated Polyolefins via Metathesis Degradation-hydrogenation of Diene Rubbers
Xi-xi Wang, Lu Dai, Su-yun Jie, Bo-geng Li
六校 , doi: 10.11777/j.issn1000-3304.2019.19171
[Abstract](171) [FullText HTML](93) [PDF 1845KB](6)
The carboxyl-terminated polydiene is a kind of widely used telechelic liquid rubber, which is commonly used as adhesive for solid rocket propellant, material bonding, sealant, electric insulation or as modifier of epoxy resins. Taking diene rubbers as raw materials, the carboxyl-terminated polydienes were synthesized via olefin metathesis degradation of diene rubbers catalyzed by Grubbs II catalyst ( G2 ) in the presence of maleic acid as a chain transfer agent (CTA). The carboxyl-terminated polyolefins were further prepared by the subsequent chemical hydrogenation with p-toluenesulfonyl hydrazide/tri(n-propyl)amine reagents. The influences of reaction conditions on the molecular weight and molecular weight distribution of products, including reaction time, reaction temperature, molar ratios of C=C/catalyst and C=C/chain transfer agent, were investigated. The results indicated that the molecular weight of products could be controlled by varying the molar ratio of C=C/catalyst or C=C/chain transfer agent. It turned out that the catalyst was highly active for the metathesis degradation of diene rubbers even if there was no existence of chain transfer agents. The structures of carboxyl-terminated polydienes and polyolefins were characterized by nuclear magnetic resonance spectroscopy (1H-NMR) and carbon spectrum (13C-NMR), infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) and their thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It’s worth noting that the trans-1,4 content of carboxyl-terminated polybutadiene via metathesis degradation greatly increased and the corresponding cis-1,4 content decreased, thus affecting the properties of polymers. After hydrogenation, the carboxyl-terminated polyolefins had better thermal stability than the carboxyl-terminated polydienes.
Synthesis of Main-chain Azobenzene Liquid Crystalline Copolyester with Cide Hydroxyl Group and Its Photoresponsive Behavior
Ya-ting Peng, Tao Wang, Hang Li, Rong Yang, Jin-chun Li
六校 , doi: 10.11777/j.issn1000-3304.2019.19177
[Abstract](179) [FullText HTML](108) [PDF 1623KB](17)
A series of main-chain azobenzene liquid crystalline copolyesters containing side hydroxyl group (Az-LCP) were synthesized with 4,4'-bis(6-hydroxyhexyloxy)biphenyl (BHHBP), 4,4'-bis(6-hydroxyhexyloxy)azobenzene (BHHAB), diethyl malate (DM) and phenyl succinic acid (PSA) by random copolymerization. Chemical structure of the Az-LCPs was characterized by proton nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). And the phase transition behavior of the Az-LCPs was characterized by differential scanning calorimeter (DSC), and X-ray diffraction (XRD). Az-LCPs showed a nematic phase with a glass transition temperature (Tg) around room temperature. With increasing BHHAB monomer, the Tg and nematic-isotropic transition temperature of Az-LCPs decreased from 25.6 °C and 96.4 °C to 19 °C and 88.2 °C, respectively, showing a trans-cis photoisomerization effect of Az-LCPs. Then monodomain azobenzene liquid crystalline networks (Az-LCNs) were prepared by uniaxial stretching at nematic phase first, postcrosslinking in the hexamethylene diisocyanate solution for 12 h. Moreover, the orientation degree decreased with increasing BHHAB monomer into Az-LCP due to the decreasing Tg and π-π stacking interaction. While being crosslinked with HDI, the Tg of Az-LCNs increased up to 40 °C, meanwhile, the nematic-isotropic phase transition became broad and almost disappeared as the BHHAB monomer increased. All the Az-LCNs showed a UV-light induced bending and vis-light induced unbending behavior at room temperature except Az-LCN4 which contains 50% BHHAB monomer. Crosslinking duration of Az-LCNs also exhibited an influence on the photoresponsive bending/unbending behavior. With increasing crosslinking duration, the bending angle increased first and then decreased. In addition, the maximum bending angle and photoresponsive speed of Az-LCNs decreased with increasing thickness of the Az-LCNs films. Az-LCP1 with 10% azobenzene content and cross-linking for 12 h exhibits excellent photoresponsive behavior with a high bending angle of 88° and the fastest photoresponsive speed.
Chain Entanglement Regulation of Sintered UHMWPE and Its Effect on Properties
Peng Dong, Ke Wang, Jun-fang Li, Qiang Fu
六校 , doi: 10.11777/j.issn1000-3304.2020.19159
[Abstract](277) [FullText HTML](138) [PDF 1227KB](47)
Ultrahigh-molecular-weight polyethylene (UHMWPE) shows outstanding toughness, wear resistance and chemical inertness as a high performance polymer. However, extremely high entanglement degree results in high viscosity and processing difficulties, which greatly limits the applications. To address this issue, the new single-site Z-N catalysts have been used to regulate the growth and cohesion of molecular chains during the polymerization of ethylene in recent years, by which nascent UHMWPE with low entanglement degree and excellent processing capability can be obtained. With such UHMWPE nascent powder, different sintering temperatures (Ts) of 170, 190 and 220 °C were set, respectively, then a isothermal crystallization step with precise temperature control was added, and the effect of chain entanglement on the structures and properties of sintered UHMWPE was investigated. Through the tensile tests at 160 °C, it was confirmed that UHMWPE chains significantly reentangled when Ts = 220 °C, resulting in high degree of entanglement; while the initial low entanglement state can be sufficiently reserved when Ts = 170 °C, Me reached 12.3 kg/mol. Therefore, the samples with distinct different entanglement states can be obtained. DSC results have shown that low entanglement degree was beneficial to the formation of crystal lamellae with higher melting temperature (up to 141 °C) and high crystallinity (up to 65%) through isothermal crystallization steps, which was close to the level of nascent UHMWPE powder. Moreover, it proved that the integrated mechanical performance of the product sintered at 170 °C was significantly improved. The yield strength was increased by up to 72%, the tensile strength by 139%, the elastic modulus by 162%, and the elongation at break by 36%, realizing simultaneously strengthening and toughening of sintered UHMWPE materials. This provides a new strategy for the high performance UHMWPE sintered products from the perspective of chain entanglement regulation.
Preparation and Properties of Recyclable High-performance Epoxy Resins and Composites
Dong Wang, Li-ying Li, Hong-jun Ke, Kong-li Xu, Shan Lu, Wenhua Gong, Huan Zhang, Guo-yong Wang, Ying-min Zhao, Ning Zhao
六校 , doi: 10.11777/j.issn1000-3304.2019.19167
[Abstract](153) [FullText HTML](72) [PDF 1359KB](15)
Aiming at the demands for recyclable resins and composites in practical applications, high performance recyclable epoxy resins with excellent comprehensive properties are prepared using methyl teterahydrophthalic anhydride as the curing agent and zinc acetylacetonate hydrate as the catalyst. The effects of anhydride and catalyst concentrations on the structure, thermal and dynamic properties of epoxy vitrimers are systematically explored to achieve the resin formulation optimization. With the decrease of anhydride concentrations, the cross-linking densities decrease, and the epoxy vitrimers show decreased glass transition temperature (Tg) but enhanced dynamic properties, which is attributed to the sufficient hydroxyl groups in structure that could trigger the transesterification exchange reactions with ester bonds. The increase of catalyst concentrations can also lead to enhanced dynamic properties as a result of the accelerated transesterification rates. The epoxy vitrimer with epoxy/anhydride/catalyst ratios of 1:0.5:0.05 displays optimal comprehensive performance with intermediate thermal properties and excellent dynamic properties. Based on the dynamic transesterification reaction, the epoxy vitrimers can be well reprocessed by the physically hot pressing methods at 180 °C for 6 h under a pressure of 10 MPa, and the recycling efficiency can be up to 80%. Moreover, the epoxy vitrimer-based carbon fiber reinforced composites are prepared by the resin transfer molding (RTM) technique. The prepared carbon fabric composites show a tensile strength of 479 MPa and tensile modulus of 58 GPa, revealing comparable mechanical properties to those of traditional thermoset composites. After heating the composites in ethylene glycol solvent at 180 °C for 8 h, the clean carbon fiber fabric with the same dimension as fresh ones can be reclaimed due to the dissolution of epoxy vitrimer binder in alcohol solvent via transesterification. In addition, the collected dissolved polymers can form vitrimers again by evaporating the EG solvent in open air at 180 °C for 12 h. It is demonstrated that the carbon fibers and epoxy polymers can both be fully recycled from the composites by the alcohol solvent dissolution method.
Interface Properties in Polymer/Single-chain Nanoparticle Composite
Hu-jun Qian, Zhong-yuan Lu
六校 , doi: 10.11777/j.issn1000-3304.2020.19152
[Abstract](299) [FullText HTML](175) [PDF 4760KB](54)
It is a practical method to control the property of polymer material by incorporating nanoparticles. Recently polymer/nanoparticle composites have drawn increasing attention in the polymer field. Although researchers have made apparent progresses in the property regulation of polymeric materials by incorporating nanoparticles, progress in the development of the corresponding theory is, however, greatly inhibited, due to the lack of proper characterization approach, especially on the interaction mechanism between various nanoparticles and matrix polymers mainly at their interface area. This mini review summarizes recent simulation results of our research group, especially on a polymer/nanoparticle composite system where nanoparticles are single-chain crosslinked polymer nanoparticles with the same chemical composition as matrix polymers. In particular, after a thorough discussion of the structure and dynamic properties at nanoparticle/polymer interface region, it is clear that the interface in this system, where nanoparticle and matrix polymer interact effectively, has approximately the same size as nanoparticle itself. This interface size has no dependence of matrix polymer chain length. We hope that this conclusion can be helpful for the further development of relevant theory for polymer/nanocomposite systems.
The Microstructures and Molecular Interactions in Multiphase Polymers: Insights from Solid-State NMR Spectroscopy
Rong-chun Zhang
六校 , doi: 10.11777/j.issn1000-3304.2019.19175
[Abstract](245) [FullText HTML](118) [PDF 4727KB](46)
In recent decades, solid-state nuclear magnetic resonance (NMR) spectroscopy has been playing an important role in the characterization of polymer materials. To some degree, it has become one of the indispensable tools for studying the microstructures, segmental dynamics and inter-/intra-molecular interactions and elucidating the structure-functionality-property relationship of multiphase polymer materials, because the anisotropic spin interactions in the molecules can be selectively manipulated via various radiofrequency pulse sequence design. As a result, NMR can provide important information on a length scale from 0.1 nm to 100 nm and a time scale from 1 ns to 100 s. Herein, in this current review article, we will review some of our recently developed solid-state NMR approaches specifically for applications in polymers, including quantitative determination of compositional contents, characterization of crosslinking/entanglement density and inhomogeneity of the network, hydrogen bonding interactions between segments, and so on. A variety of typical examples, including self-healing supramolecular rubbers, thermal reversible polyurethanes, dual-cross-linked hydrogels, elastomers, etc., are given in detail, showing how various solid-state NMR approaches were implemented to quantitatively characterizing the structures, molecular interactions, and crosslinking network. Furthermore, due to the presence of heterogeneous dynamic in multiphase polymers, the applications of traditional solid-state NMR techniques are sustainably limited, and we also developed corresponding novel solid-state NMR approaches to overcome the limitations and enhance the spectral resolution and signal sensitivity.
Strain-induced Crystallization of Long Chain Polyamide and Its Copolymers
Li-li Wang, Ping Zhu, Xia Dong, Du-jin Wang
六校 , doi: 10.11777/j.issn1000-3304.2020.19165
[Abstract](303) [FullText HTML](137) [PDF 3102KB](35)
As a special species of polyamide, long chain polyamide (LCPA) provides combined performances of polyolefin and polyamide due to its chemical structure with long methylene chains segments between two neighbor polar amide groups. During the processing or application, strain-induced crystallization (SIC) has a significant effect on the mechanical strength and elasticity of LCPA and LCPA based its copolymers. It is of great importance to further study the microstructural evolution mechanism for the design and production of LCPA and its copolymers under the external field. With a focus on the SIC, this feature article mainly summarizes our group’s work on SIC of LCPA since 2010 and some related studies of other researchers, including the phenomenon of SIC observed in LCPA and its copolymer, the influencing factors of SIC and the corresponding rules, the correlation between SIC and the mechanical properties, and the characterization technics as well.
Material Research Progress of the Sustainable Polymer-Cellulose
Bo Duan, Hu Tu, Li-na Zhang
六校 , doi: 10.11777/j.issn1000-3304.2020.19160
[Abstract](415) [FullText HTML](242) [PDF 5666KB](75)
The " Green Chemistry” has become the strategy direction of research and development of the world in the 21th century. Cellulose, as the most abundant natural polymers, is a very important renewable resource and the main industrial raw material. The cellulose shows many great advances including biocompatibility, biodegradability, high structure stability. However, due to the large amounts of inter- and intra-hydrogen bonding among the cellulose molecules, the cellulose has a dense structure and is very hard to be processed through dissolution or melt, which limit the further exploitation of the cellulose resource. The traditional organic solution of the cellulose often has the problem of high cost and pollution. In recent decades, with the development of the " Green” solvent (alkaline/urea, ionic liquid, etc.) and the cellulose nanotechnology, the researchers have greatly expanded the cellulose application in biomedical, energy storage, optical fields in addition to the traditional spinning and papermaking industry. This review mainly introduces the new methods (" bottom to up” and " up to down”) for the exploitation of cellulose based materials in recent years through the following four sections: (1) the regenerated cellulose based materials from the " green” solution-alkaline/urea aqueous and ionic liquid; (2) the preparation and self-assembly of the nanocellulose; (3) the development and utilization of the wood nanotechnology; (4) bacterial cellulose based functional materials.
Cationic Surfactant Sensor Based on Polyacrylic Acid Two-dimensional Photonic Crystal Hydrogel
Xia-tong Qin, Gen-qi Liu, Chen-hui Liu, Jian-xun Liu, Huan-huan Li, Yun-lei Cao, Xiao-dong Fan
六校 , doi: 10.11777/j.issn1000-3304.2019.19170
[Abstract](202) [FullText HTML](92) [PDF 1082KB](18)
A polyacrylic acid two-dimensional photonic crystal hydrogel (PAA 2D-PCH) was prepared with acrylic acid as monomers, ethylene glycol dimethylacrylate as cross-linkers, 2,2-diethoxyacetophenone as initiators and polystyrene two-dimensional photonic crystal with bright diffraction under visible light illumination as a template, and its stimulating response properties to cationic surfactants were investigated. The results indicated that the PAA 2D-PCH had a sensitive response to cationic surfactants, while no response to anion, nonionic and zwitterionic surfactants. When the concentration of CPC, CPB and CTAB was increased from 0 to 4 × 10−3 mol/L, the diameter of Debye ring increased by 5.95, 5.50 and 4.95 cm, respectively, and the particle spacing decreased by 390, 364, and 341 nm, respectively. In the anionic surfactant, nonionic surfactant and zwitterionic surfactant solution, the diameter of Debye ring of the PAA 2D-PCH showed almost no change. The selective recognition of cationic surfactants by PAA 2D-PCH stemed from the electrostatic interaction between the negatively charged carboxylate ions and the cationic surfactants in the phosphate buffer solution of pH = 7.4, causing the PAA 2D-PCH shrunk, the particle spacing reduced, the diameter of the Debye ring increased, and the diffraction wavelength blue shifted. Study on the response behavior of PAA 2D-PCH to cationic surfactants by Debye ring method is easy to operate and has the characteristics of reusability and visualization, which is expected to be used for the determination of cationic surfactants in water.
Typical Polymer Fiber Materials: An Overview and Outlook
Sen-long Yu, Heng-xue Xiang, Jia-liang Zhou, Tian Qiu, Ze-xu Hu, Mei-fang Zhu
六校 , doi: 10.11777/j.issn1000-3304.2020.19148
[Abstract](429) [FullText HTML](291) [PDF 3014KB](42)
High molecular material (or abbreviated as polymer) is the substantial foundation of human survival and development, which is regarded as the important symbol of social civilization. Polymer materials usually can be divided into plastic, fiber and rubber according to the application fields and molecular weight. Among them, polymer fibers are defined as the thin strip shaped materials with the length-diameter ratio larger than 1000 (usually a nanoscale or micron-scale diameter) and certain tensile strength and toughness. With the development of society and the progress of science and technology, the application fields of polymer fibers are gradually expanded from traditional home textile and clothing to advanced fields such as aerospace, biomedicine, environment, energy and so on. Therefore, the product connotations and applications of polymer fiber materials are expanding continually, which are the basic materials of national economy, the strategic materials of national defence, the frontier materials of emerging industries. In this work, we briefly introduced the development history of polymer fiber materials firstly, which have experienced the natural fiber, artificial fiber, synthetic fiber, functional fiber and high-performance fiber stages in turn. Then, the present situation of several representative polymer fiber materials (such as common fiber-polyethylene terephthalate fiber, high performance fiber-polyphenylene sulphide fiber, biomass fiber-poly lactic acid fiber) were introduced systematically based on our group’s research work, including the development history, fabrication methods, chemical and physical structures and properties, modification technologies and application fields. In the end, we put forward the future prospect of polymer fiber materials combined with the social development demand. Based on the interdisciplinary integration and technological breakthroughs of materials, information, biology, machinery and other disciplines, the polymer fiber material (called Next Generation Fiber) with multiple components, multiple structures and multiple functions will become future development trend, which are characterized by green, super performance and intelligence.
Applications of Polymeric Micro/Nanoparticles in Engineered Vaccines
Hua Yue, Guang-hui Ma
六校 , doi: 10.11777/j.issn1000-3304.2019.19143
[Abstract](377) [FullText HTML](188) [PDF 2741KB](54)
With the increasing demand for preventing and controlling of new/sudden diseases, major infectious diseases and malignant tumors, vaccines that based on traditional experience await updated. In terms of the unique physio-chemical advantages, polymeric micro/nano particles have become the research hotspots in the field of biomedical delivery. However, the rational integration of the micro/nano particles into vaccine delivery system is a huge challenge. On the basis of our research on the preparation and application of polymer micro/nano particles, an advanced strategy that co-assembles the particle "chassis" and subunit vaccines into one engineered vaccine is proposed. During the 20-year systematic study, new functions of polymeric particles are developed, and important mechanisms for the enhanced cellular/mucosal immunity are clarified. Apart from the chassis with conventional physiochemical property, other chassises with lysosomal escape merit, unique properties (deformability or mobility), or " Immunoticket” advantage have been exploited. The present paper not only summarizes our work but also involves international research progress, which sheds light upon the engineered vaccine chassises for their on-demand design concept, relative mechanism and development
Preparation and Characterization of Electrospinning Crosslinked Gel Polymer Electrolytes
Yun-ni Chen, Qin Xiao, Qing-yin Li, Shi-jie Ren
六校 , doi: 10.11777/j.issn1000-3304.2019.19149
[Abstract](285) [FullText HTML](142) [PDF 1449KB](30)
Gel polymer electrolytes (GPEs) for lithium ion batteries (LIBs) have attracted great attention due to their high ionic conductivity and safety, but it is still a great challenge to develop GPEs which can be used at high temperature in specific applications, such as oil drilling, mining, military and aerospace electronics. Cross-linking is one of the efficient methods for enhancing the thermal stabilities of GPEs. In this work, crosslinked gel polymer electrolytes (e-CGPEs) were made by electrospinning and Friedel-Crafts alkylation reaction. First of all, electrospun polymer membranes (e-PMs) were prepared by electrospinning technique with poly(vinylidene fluoride) (PVDF) as the matrix and polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-PEO-PS) triblock copolymer as the additive. Then the styrene units in e-PMs were crosslinked by Friedel-Crafts alkylation reaction to give electrospun crosslinked polymer membranes (e-CPMs). e-CPMs were activated by absorbing electrolytes to give crosslinked gel polymer electrolytes (e-CGPEs). The effects of PS-PEO-PS content (3%, 5%, 10%, 20%) on the properties of e-CPMs and e-CGPEs were also discussed. The results show that the content of PS-PEO-PS can affect the crystallinity, electrolyte uptake and crosslinked degree of e-CPMs, which may have influences on the ionic conductivity. Owing to the abundant crosslinked networks, high-temperature dimensional stabilities of e-CPMs are much better than that of electrospun PVDF membrane and commercial polypropylene (PP) membrane. All e-CPMs show almost no dimensional shrinkage at 160 °C, indicating that e-CPMs can be efficient precursors of GPEs used at high temperature. e-CGPEs have better electrochemical performances than the PVDF-based GPE (e-PVDF), due to their high porosity, electrolyte uptake and ionic conductivity. Among all the e-CGPEs, e-CGPE 5% with proper PS-PEO-PS content and crosslinked degree possesses the highest ionic conductivity of 6.52 mS/cm at room temperature. The half-cell assembled by e-CGPE 5% shows a discharge specific capacity of 83.5 mAh/g at 2 C. e-CGPEs also exhibit excellent cycle and rate performances. e-CGPE 5% has a capacity retention of 99.7% after 100 cycles at 0.1 C. All the results suggest that e-CGPEs have potential application value in high-efficiency lithium ion batteries which could be used at high temperature. And this work also provides a new path for the preparation of crosslinked gel polymer electrolytes with high efficiency and good performance.
Application of Molecular Simulation in the Study of Polyimide
Huan-yu Lei, Guo-feng Tian, Mei-feng Xiao, Xiao-lan Li, Sheng-li Qi, De-zhen Wu
六校 , doi: 10.11777/j.issn1000-3304.2019.19157
[Abstract](341) [FullText HTML](225) [PDF 1112KB](42)
Featured by its outstanding thermo-oxidative stability and excellent mechanical properties, polyimide has aroused growing research interests. The hierarchical structure of polyimide (PI), which largely influences its thermal, mechanical, and photoelectric properties, can be well adjusted by carefully regulating the chemical composition. In this review, we primarily focus on the employment of molecular simulation for unravelling and interpreting the structure-property relationship of PI materials, and summarize the recent progress both at home and aboard on the research of multi-scale PI structures. The molecular chain structures of PI can be finely analyzed in terms of the chains conformation, characteristic ratio and torsion energy barrier, while the thermal and mechanical properties are properly explained from the perspective of molecular chain constitutions, chains movement and the packing state of PI chains. Meanwhile, the highly concerned force field has been used in molecular dynamic (MD) simulation of PI thermal-mechanical behaviours. MD simulation or Monte Carlo (MC) simulation also works well for understanding the gas separation performance of PI materials through the fractional free volume (FFV) of PI molecules or the dissolution and diffusion patterns of small molecules in novel PI framework with particular main-chain or side-chain structures. Furthermore, the studies on PI-based composites are basically concentrated on the exploration of interfacial properties between PI and other materials, including the simulated binding energy and small-scale interactions like the van der Waals forces and electrostatic interactions. The development trend of computer simulation in PI-related research is briefly discussed in the end, so as to provide valuable guidance for the performance optimization of PI materials as well as some useful thoughts on the design and preparation of functional PI molecules.
Synthesis and Property of Novel Functionalized Polytetrahydrofuran-b-polyisobutylene-b-polytetrahydrofuran Triblock Copolymers
Fang Zhang, Hang-tian Zhang, Tian Yang, Bo Kong, An-Ru Guo, Qi Zhang, Yi-xian Wu
六校 , doi: 10.11777/j.issn1000-3304.2020.19151
[Abstract](334) [FullText HTML](158) [PDF 2378KB](32)
The functionalized polyisobutylenes (PIBs) carrying allyl-Br or allyl-NH2 with different molecular weights and narrow molecular weight distribution, could be successfully synthesized via controlled/living cationic polymerization of isobutylene (IB) in n-hexane/CH2Cl2 mixed solvents at −80 °C. Controlled/Living cationic ring-opening polymerization (ROP) of tetrahydrofuran (THF) was achieved with Allyl-Br/AgClO4 initiating system at 0 °C. Two kinds of novel functionalized PTHF-b-PIB-b-PTHF triblock copolymers were designed and synthesized via combination with controlled/living cationic polymerization of IB and controlled/living cationic ROP of THF. Terminal hydroxyl functionalized HO-PTHF-b-PIB-b-PTHF-OH triblock copolymers (expressed as FIBF-OH) were successfully synthesized by using the PIBs with difunctional allyl-Br terminal groups (Br-PIB-Br) as macroinitiators to initiate living cationic ROP of THF in the presence of AgClO4 to create living PTHF+-b-PIB-b-PTHF+ chains and then terminating by H2O molecules. On the other hand, PTHF-b-HN-PIB-NH-b-PTHF triblock copolymers containing hydrogen bonds at the connection point of PTHF and PIB segments (expressed as FIBF-NH) were also successfully synthesized via efficient nucleophilic substitution reaction between living PTHF+ chains and amine groups in H2N-PIB-NH2. Due to the dynamic incompatibility between polar PTHF segments and nonpolar PIB segments and the crystallization of PTHF segments, PTHF-b-PIB-b-PTHF triblock copolymers exhibit an obvious microphase separation micromorphology. It is recognized that the chemical structure in the PTHF-b-PIB-b-PTHF triblock copolymers makes a great contribution to the formation of hydrogen bonding and thus the supramolecular network. The crystallization of PTHF segments could be improved even in FIBF-NH with relatively short PTHF segments, e.g. Mn,PTHF = 0.7 kg·mol−1. FIBF-NH could be completely self-healing at 25 °C for 10 min after cutting on its surface. However, the cutting on FIBF-OH surface was difficult to heal even at 30 °C for 3 days. Moreover, the PTHF-b-PIB-b-PTHF triblock copolymers could be used as drug carrier by interactions between PTHF segment and drug. The drug carrier microspheres exhibit pH-sensitive drug-release rate in PBS with different pH values. The novel functionalized PTHF-b-PIB-b-PTHF triblock copolymers combined the respective good properties from PIB and PTHF segments would have their potential applications as biomedical and smart-healing functional materials.
Graphyne and Modified Graphyne in the Fields of Photoelectrocatalysis and Photovoltaics
Jia-bin Zhang, Jia-liang Xu, Bao Zhang, Ya-qing Feng
六校 , doi: 10.11777/j.issn1000-3304.2019.19153
[Abstract](344) [FullText HTML](139) [PDF 1872KB](41)
Different from other members in the carbon material family, graphyne, first synthesized in 2010, has sp hybridized carbons and a natural band gap. According to many studies on optoelectronic devices, the recombination of electrons and holes is an important issue, and the excellent photoelectric properties of graphyne such as high carrier mobility and π-conjugated structure can make it an important candidate material in the fields of photocatalysis, electrocatalysis, batteries, etc. However, there are still problems remaining for the direct application of unmodified graphyne owing to its inert surface and fixed band gap. The high activity of acetylenic bond units in the graphyne provides a good platform for chemical modification and doping. Therefore, the energy band structure and semiconductor performance of graphyne can be regulated by simple solution mixing, hydrothermal reaction, and redox method to achieve material hybridization or hetero atom doping, so that the graphyne will fulfill the requirements of photoelectric devices for a semiconductor material. Many studies have been concentrated on this topic, and numerous achievements have been made over the years. In this review article, the properties and synthesis methods of graphdiyne are firstly introduced, followed by a systematic summary about the mechanism of different atomic doping changes which could help in design of precursor molecules and subsequent synthesis of graphyne derivatives. The promotion effect of graphyne hybridization on charge transfer and its specific mechanism are then detailedly illustrated. The latest research progresses of graphyne and graphyne derivatives in practical applications including photoelectrocatalysis, dye sensitized solar cell, and perovskite solar cell are further discussed, while some problems existing in the current research of this field are also listed. Our review concludes with the proposal that research focuses in the future should be shifted from theoretical calculation to specific experiment and the mechanism in the process requires better understanding, so as to push forward the studies on graphyne and further improve material properties.
Measuring the Strength of S/Se Based Dynamic Covalent Bonds
Jia-hao Xia, Hong-bin Li, Hua-ping Xu
六校 , doi: 10.11777/j.issn1000-3304.2019.19166
[Abstract](507) [FullText HTML](304) [PDF 1391KB](38)
Sulfur, selenium-containing bonds, including disufide bond (SS), diselenide bond (SeSe), and selenide-sulfide bond (SeS), are an important type of light responsive dynamic covalent bonds. Among them, SS and SeS bonds can undergo exchange reaction with the irridiation of UV light, while SeSe bond only requires visible light due to its weaker bond energy. The purpose of this research is to use atomic force microscope-based single molecule force spectroscopy (AFM-SMFS) measurement to reveal the reasons behind the responsiveness and stability of S/Se related dynamic covalent bonds. In this study, quartz substrates modified by SS or SeSe bond were prepared via surface modification. Specifically, the quartz substrates were first washed with a mixture of sulfuric acid and hydrogen peroxide (volume ratio is 7:3), and then processed with oxygen plasma to obtain a hydrophilic surface. The surface then reacted with 3-aminopropyltriethoxysilane to form amino groups at the top, which further reacted with disulfide or diselenide containing diacid to afford SS or SeSe bond-modified substrates. The structures of the surfaces were comfirmed by water contact angle (WCA), atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry. Based on the light induced exchange reaction, wettabilities of the substrates were able to adjusted and were characterized by WCA and XPS. By exchanging with thiol or diselenide containing polymer, the polymer chain-attached substrates linked by a single bond of either SS, SeS, or SeSe could be obtained. The rupture forces of the three bonds were measured by SMFS. At a pulling speed of 200 nm/s, the rupture forces of SeSe, SeS and SS bonds were (1100 ± 300), (1320 ± 330), and (1450 ± 300) pN, respectively, indicating their strengths decreased as SS > SeS > SeSe. This result was consistent with the thermodynamic stability ranking of the three bonds. SMFS results illustrated that the strength of the dynamic covalent bond is between that of non-covalent interaction and that of robust covalent bond (e.g. C―C bond), which accounts for its balance of responsiveness and stability.
A Discussion on the Origins and Development of Polymer Physics
Yu-liang Yang, Hong-dong Zhang
六校 , doi: 10.11777/j.issn1000-3304.2020.19162
[Abstract](312) [FullText HTML](190) [PDF 0KB](15)
In this paper, we briefly review the origins and growth of polymer physics from our perspective. It is proposed that the theory of rubber elasticity can be regarded as a starting point of polymer physics. It reveals why many mainstream theories can work and play key roles in the history of polymer science. We hope researchers may take their impetus from the achievement of classic and modern polymer physics.
Polyelectrolyte Complexes-based Hydrogels with High Mechanical Strength and Excellent Self-recovery
Tao Yuan, Jun-qi Sun
六校 , doi: 10.11777/j.issn1000-3304.2019.19093
[Abstract](909) [FullText HTML](457) [PDF 1102KB](87)
Polymeric hydrogels with high mechanical strength and excellent self-recovery are useful in tissue engineering, stretchable electronics and wearable devices. In this work, polyelectrolyte complexes-based hydrogels with high mechanical strength and excellent self-recovery are fabricated by complexation of poly(vinyl alcohol) modified with benzaldehyde-2,4-disulfonic acid disodium salt (BADS) (denoted as SPVA) with linear poly(ethylenimine) (LPEI) in aqueous solution followed by molding, drying and rehydration. The mechanical properties of the LPEIa/x%-SPVAb hydrogels, where x% represents the molar ratio of BADS to the monomer molar ratio of PVA, and a and b represent the feed mass ratio of LPEI to SPVA, can be well-tailored by varying the parameters such as the grafting ratio of BADS on SPVA and mass ratio of LPEI to SPVA. Stress-strain measurements indicate that the LPEI1/18%-SPVA1 hydrogels have the highest mechanical strength, with a tensile strength of ~ 10.0 MPa and a toughness of ~ 14.21 MJ/m3. A piece of the LPEI1/18%-SPVA1 hydrogel strip with a width of 2 mm and thickness of 2 mm can sequentially withstand various deformations such as bending, knotting, and twisting, and can lift a 1 kg weight without any damage. Besides the electrostatic interactions between sulfonate groups of SPVA and protonated amine groups of LPEI, Fourier transform infrared spectroscopy confirms the existence of hydrogen-bonding interactions between hydroxyl and sulfonate groups on SPVA. The synergy of strong electrostatic interactions and weak hydrogen-bonding interactions endows the hydrogels with high mechanical strength and toughness. Moreover, the hydrogels can completely recover from a strain of 200% to their original shape and mechanical properties within 1 h rest at room temperature without any external assistance. The excellent self-recovery of the LPEI1/18%-SPVA1 hydrogels originates from the high elastic retraction of polymer chains arising from electrostatic interactions and the reversibility of sacrificial hydrogen-bonding interactions. The high mechanical strength and excellent self-recovery will make the hydrogels have potential applications in aspects such as load-bearing materials, actuators and stretchable electronics.
Theoretical Models for Stress-Strain Curves of Elastomer Materials
Fang Ding, Huan Zhang, Ming-ming Ding, Tong-fei Shi, Yun-qi Li, Li-jia An
六校 , doi: 10.11777/j.issn1000-3304.2019.19132
[Abstract](755) [FullText HTML](420) [PDF 959KB](80)
Based on the analysis of uniaxial stress-strain curves, the quantitative relationship between the composition, structure and properties of elastomers can be obtained. So far, more than 30 constitutive models have been developed. Here, we summarized the fundamental assumptions, boundary conditions, general ranges for model parameters and the characteristics of stress-strain curves of these typical models. Equations associated with phenomenological models, statistical mechanics models and their deviations were listed. Through the analysis of the best non-linear fitting of these modeling stress-strain curves using the coefficient of determination and Fréchet distance, the similarity and mathematical equivalence of models were quantified. It was found that Gent model and Warner model, Three-Chain model and Eight-Chain model have mutual equivalence in the depiction of stress-strain curves with strain hardening. Other models can undirectionally replace some models with less parameters and computational complexity. This work can help the selection of the proper constitutive models to simulate complex stress-strain behaviors of elastomer materials.
Studies on Homo- and Co-polymerizations of Polar and Non-polar Monomers Using Rare-earth Metal Catalysts
Dong-mei Cui
六校 , doi: 10.11777/j.issn1000-3304.2020.19142
[Abstract](304) [FullText HTML](304) [PDF 3639KB](62)
The homo- and co-polymerizations of polar and non-polar monomers, since they can remain the stereo-regularity of the non-polyolefin precursors and meanwhile introduce polar groups into the non-polar polyolefins to improve their surface properties or bring unpredicted new functionalities, have attracted great attention of both academia and industries. However, polar groups are Lewis-basic while the catalysts employed in the polymerizations are usually Lewis acidic, which are prone to interact with the catalytic metal center to poison the catalysts, thus the study on homo- and co-polymerizations has been a challenging project. To date, many achievements have been obtained, and the following research should focus on realizing the homopolymerizations of polar monomers, increasing the activity and insertion ratio of the polar monomer in the copolymers, regulating the polar monomer composition and distribution along the copolymer macromolecular chains and isolating high molecular weight and practically available products. In this review, we summarized the recent developments of our group on the homo- and co-polymerizations of polar monomers, in particular polar styrenes and conjugated dienes with styrene, ethylene, butadien, isoprene and other popular nonpolar olefins, aiming to provide the readers novel strategies for designing new catalysts and polar monomers, as well as the unprecedented mechanisms.
Preparation and Bio-medical Applications of Dynamic ChemistryBased Self-healing Hydrogels
Yong-san Li, Yan-shuang Xu, Lei Tao, Yen Wei
五校 , doi: 10.11777/j.issn1000-3304.2020.19144
[Abstract](531) [FullText HTML](351) [PDF 4343KB](106)
Self-healing hydrogel is a new generation smart material that has drawn great attention among researchers from multiple cutting edge areas. Self-healing hydrogels are continuously enriching our knowledge in developing new materials and changing our lives. In the recent decades, thanks to numerous dedicated researchers, series of self-healing hydrogels have been explored through dynamic chemistry and supramolecular interactions, which have been applied in interdisciplinary areas for controlled release of drugs, 3D cell culture, and scaffolds of tissue engineering, etc. Self-healing hydrogels can be injected as solid gels instead of liquid precursor, then self-heal in situ. Thus, self-healing hydrogels have been utilized as a new type of injectable carrier to deliver drugs. This method effectively avoids unwanted cargo loss throughout the cycling and dramatically improves the delivery efficiency of drugs. Thus, self-healing hydrogels have been studied in recent research as great therapeutic carrier for tumour therapy and wound-healing. This review aims to summarize some recent research progresses in the preparation of self-healing hydrogels based on different dynamic covalent bonds. The bio-medical applications of self-healing hydrogels including tumour therapy and wound-healing have also been introduced. The future development and challenges of dynamic chemistry based on self-healing hydrogels have also been discussed.
Regioselective Polymerization of α-Methylene β-Butyrolactone: Synthesis of Linear and Cyclic Polyesters
Yue-chao Xu, Hui Zhou, Xiao-bing Lv
六校 , doi: 10.11777/j.issn1000-3304.2020.19145
[Abstract](488) [FullText HTML](400) [PDF 959KB](22)
Regioselective polymerization of α-methylene β-butyrolactone (MβBL) to afford polyesters with various topological structures was achieved by the use of different catalysts or initiators. With azodiisobutyronitrile (AIBN) as initiator, polymerization selectively occurred at the C=C bond to produce linear poly(α-methylene-β-butyrolactone) (PMβBL) with the remain of β-butyrolactone unit. Achiral Salen aluminum complexes afforded linear syndiotactic-enriched polyesters with controllable molecular weight and a narrow polydispersity, in which ring-opening polymerization selectively occurred at the acyl C―O bond of MβBL and the C=C bond was remained. Strong organic bases, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), exhibited high activity for ring-opening polymerization of MβBL under mild condition, affording linear polyesters. Simple sodium iodide mediated MβBL polymerization predominately produced crystalline cyclic polyesters with a melting point of 145.4 °C, in which the ring-opening mainly concerned the alkyl Cβ―O bond cleavage. This study demonstrates that the synthesis of various topological materials with different properties can be achieved by regioselective polymerization of functional monomers with the exquisite choice of catalyst or initiator.
Particle Morphology Control of Polypropylene Heterophasic Copolymer at Increased EPR Content by Simultaneous Cross-linking
Meng-jia Zhang, Li Wang, Liu-ting Hong, Ya-wei Qin, Jin-yong Dong
三校 , doi: 10.11777/j.issn1000-3304.2019.19115
[Abstract](640) [FullText HTML](239) [PDF 1372KB](50)
Heterophasic copolymerization of propylene based on MgCl2-supported Ziegler-Natta catalysts, that is, sequential propylene homopolymerization or copolymerization with minor amount of ethylene followed by ethylene/propylene random copolymerization for EPR, is a major polymerization technique in polypropylene industry, whose products, depending on their EPR contents, include high impact PP (hiPP, where EPR weight fraction is normally less than 40%) and thermophastic olefin elastomer (TPO, where EPR weight fraction is higher than 50 wt%). Compared to hiPP, the production of TPO is rather more challenging, for increased EPR contents makes it very difficult to prevent EPR from overflowing to the surfaces of the polymer particle, which will mess up with the particle morphology and lead to serious reactor fouling issues, affecting the production continuity. How to control the particle morphology at increased EPR contents with EPR being authentically contained inside without contaminating the surfaces has become a key scientific issue in further developing heterophasic copolymerization of propylene to TPO. This paper reports that the solution may lie in a simultaneous cross-linking of EPR using nonconjugated α,ω-diolefin during its polymerization. It is shown that simultaneous cross-linking can alter EPR’s viscoleastic properties to a great extent, exponentially increasing its low-shear viscosity and elasticity. As a result, EPR no longer poses as aggregated volatile droplets but rather large-size phase domains are formed by hot-compression; instead, it features dispersed particles discrete to each other. In turn, no overflowing of EPR occurs to the polymer particle surfaces. This research provides a solution for heterophasic copolymerization of propylene and polypropylene thermoplastic elastomer with high EPR content.
Fabrication of a La-based Metal Organic Framework and Its Effect on Fire Safety and Thermal Stability of Polycarbonate
Ting Sai, Shi-ya Ran, Zheng-hong Guo, Zheng-ping Fang
六校 , doi: 10.11777/j.issn1000-3304.2019.19108
[Abstract](695) [FullText HTML](310) [PDF 1444KB](25)
A La-based metal organic framework (La-BDC) was synthesized by a solvothermal method and then compounded with polycarbonate (PC) to prepare PC/La-BDC composites. The experimental (TGA, cone, vertical burning test, etc.) results showed that La-BDC improved the fire safty and thermal stability of PC. Compared with the neat PC, 2 wt% La-BDC could increase the two maximum decomposition temperatures (Tmax1 and Tamx2) of PC in air atmosphere by 43 and 40 °C, respectively; 4 wt% La-BDC could reduce the values of peak heat release rate (PHRR) and average specific extinction area (ASEA) by 50% and 38%, respectively. PC/LaD-4 composites reached UL-94 V-0 rating in vertical burning test. On the one hand, naked La metal ion cluster, as a coordinated center, afforded La-BDC activity in catalytic oxidation, isomerization reactions etc., imparting it the ability to catalyze char formation (cross-linking) in the combustion and degradation process of PC matrix. From SEM images and Raman spectrum, the denser and highly graphitized char layers were obtained. The char layers reduced the contact between the matrix and oxygen, effectively suppressing the spillover of heat, pyrolysis products and toxic fumes. On the other hand, the rod-like crystal structure of La-BDC and the mesopores contained in its own framework structure made it play a role in adsorption and retarded of smoke generation.
Design of Low-viscosity Silicon-containing Arylacetylene Resins by a Combination Screening Method
En-bin Zhou, Li-quan Wang, Jia-ping Lin, Jun-li Zhu, Lei Du, Shi-feng Deng, Jia-bin Gu, Liang-shun Zhang
六校 , doi: 10.11777/j.issn1000-3304.2019.19104
[Abstract](626) [FullText HTML](483) [PDF 1049KB](52)
It is challenging to improve the processing performance of silicon-containing arylacetylene resins while ensuring their excellent thermal properties. In this work, we presented a combination screening method for designing low-viscosity silicon-containing arylacetylene resins. We first defined the dichlorosilane as the gene for combination in terms of the chemical synthesis routes. The genes are combined with alkynyl benzene to generate a series of candidate resins. Then the viscosity, density, and thermal decomposition temperature of the candidate resins were calculated by molecular connection index method. Two optimal resins (ESA-e and ESA-2e) with higher index were screened through defining an index––a ratio of thermal decomposition temperature to viscosity. To validate the screened results, molecular dynamics simulation was used to evaluate the properties of the two optimal resins. In addition, a comparision between the optimal resins and a tranditional resin (PSA-H) were made. It was found that the viscosity of the optimal resins is lower than that of PSA-H and that of ESA-2e is the lowest. However, the glass transition temperature of the optimal resins decreased. To improve both the thermal properties and processing performance of the resins, the optimal resins were blended with PSA-H. The viscosity, thermal properties, and mechanical properties of the blends were examined by MD simulation. The results suggested that both the thermal properties and processing performance of the resins can be balanced via blending. The work provided a rapid method for the design and development of new resins. Moreover, the combination screening method can be generalized to the design of other advanced polymers.
Computer Simulation of a Single Polymer Chain Translocating through a Pore in an Asymmetric Particle Bath
Yan Wang, Wen-jie Wang, Yi-qi Xia, Hui-shu Li
六校 , doi: 10.11777/j.issn1000-3304.2019.19107
[Abstract](534) [FullText HTML](255) [PDF 855KB](34)
Polymer translocation through a nanopore is of ubiquitous importance in many biological processes such as DNA and mRNA translocation through nuclear pores, protein transport across membrane channels. In real systems, polymer translocation process usually involves complex environments. One typical example is that there present different environments inside and outside the nanopore. It is interesting to study polymer translocation in an asymmetric environment. Here, Langevin dynamics simulation is performed to study polymer translocation through nanopore in an asymmetry bath of active particles and passive particles. The polymer is modeled by a bead-spring chain and the active particle is modeled by active Brownian particles with inherent orientation. We find that with the increase of the particle activity, the translocation probability of polymer chain toward active bath increases quickly, and finally reaches a saturation value. This may be because active particles exert a drag force on the polymer chain. Additionally, as the bath activity increases, the mean translocation time of polymer chain decreases fast and then increases slightly. The physical mechanism of the non-monotonic change is that the increase of the bath activity will induce the increase of tension in polymer chain, resulting in a drag force toward active region. However, when the bath activity is large enough, crystalline layers of active particles are formed near the boundary, which inhibits the motion of active particles and increases translocation time of the chain. Furthermore, it is found that the profile of translocation time at small active force can be fitted by log-normal distribution. Moreover, we also pay attention to the length effect of polymer chain on translocation mechanism at moderate active forces. The longer polymer chain and the higher activity of particles can lead to a larger value of drag force on the polymer chain. The results may provide an insight into the translocation behavior of polymer chain, and help understand the non-equilibrium processes in living organisms.
Solvent-induced Conjugated Polymer Coils and Reversible Supramolecular Gels in Polyphenylene Ethylene Derivatives
Dong-lian Zhang, Ju-xin He, Xue-hong Zhou, Nan Zheng, Lin-lin Liu, Zeng-qi Xie, Yu-guang Ma
六校 , doi: 10.11777/j.issn1000-3304.2019.19103
[Abstract](585) [FullText HTML](506) [PDF 1272KB](54)
Good solubility is the premise in solution processing of conjugated polymers while strong π-π interaction in the main chain is generally the main cause for bad dissolution. In this paper, our strategy is intruducing the auxiliary solvent and repeat unit with the similar structure as solvent in the main chain for good solubility of conjugated polymer. Based on the well dissolution between the auxiliary solvent and polymer repeat units induce a quasi-single polymer chain and advanced self-assembly, conjugated polymer coils and reversible supramolecular gels were acheived. R-limonene was added into chlorobenzene as the auxiliary solvent for the well solubility of poly(2-(4-(3',7'-dimethyloctylo-xyphenyl)-1,4-pheny-lene-vinylene (P-PPV). Atomic force microscopy (AFM) images of the spin-coated films with solutions of low concentration showed the isolated P-PPV polymer coils and the fine structure inside the coils in chlorobenzene/R-limonene mixture; while with the absence of R-limonene, the packing of sub-polymer chain was clearly observed. In concentrated solution, P-PPV formed a reversible supramolecular gel at the concentration of 2 mg mL−1 with good temperature response characteristics in chlorobenzene/R-limonene mixture, and the gel temperature of P-PPV is in the range of 55 °C to −35 °C. Aggregations with different curvatures were obtained in different solvents, which made us further understand the pliability of conjugated polymer. P-PPV molecular chains were dissolved by the enhanced solubility of alkyl sidechain and phenylene ethylene, that made it became pliable and then entangled, which allowed the assembly of polymer coils with high curvature and supramolecular gel with high ratio of solvent wrap. The fluorescence quantum yield and fluorescence lifetime were both improved in conjugated polymer coils and reversible supramolecular gels, but the physical cross-linking points by π-π interaction showed low energy level as those of charge trap sites, where the mobility became lower. In the organic light emitting diodes (OLED), the uniform physical cross-linking network made the structure of P-PPV more stable and could effectively improve the stability, brightness, and lifetime of the device.
Phase Transition and Fluorescence Emission Characteristics ofMulti-responsive Copolymer of Oligo(ethylene glycol)Methyl Ether Acrylate and Methylacrylic Acid
Xiao-jing Dong, Hong-yan Cao, Xu-bao Jiang, Xiang-zheng Kong, Shu-sheng Li
六校 , doi: 10.11777/j.issn1000-3304.2019.19106
[Abstract](465) [FullText HTML](236) [PDF 912KB](20)
Multi-responsive polymers, with cluster-induced luminescence (CIE) featured by non-conjugated chromophores, have attracted great attention in recent years, and the relevant studies have been focused mainly on the polymers with aliphatic amines and carbonyl groups. Although the CIE behaviors of ethylene glycol-based polymers have been previously reported, studies that correlate their luminescent properties with their stimuli-responsiveness are rarely available. In this paper, P(OEGA-MAA), a copolymer responsive to temperature, pH and salt, was prepared by free radical copolymerization of oligo(ethylene glycol) methyl ether acrylate (OEGA) with methylacrylic acid (MAA) in ethanol. The structure of P(OEGA-MAA) was characterized by 1H-NMR and its molecular weight was determined by GPC. The evolution of light transmittance of the water solution of P(OEGA-MAA) with temperature was measured under different conditions and its fluorescence performance was characterized. The results show that P(OEGA-MAA) not only has responsive to temperature, pH and salt, but also emits visible blue fluorescence under UV. Effects of the polymer composition, pH and salt concentration on the lower critical solution temperature (LCST) and fluorescence properties are studied. And the relationship between fluorescence properties and phase transition process is also describled. As OEGA content decreased in the polymer, the LCST in its aqueous solution (2.0 mg/mL, pH=1) decreased, and the corresponding fluorescence intensity increased first with OEGA content up to 33 mol% (OEGA/MAA = 3.3/6.7, sample P7 ), where it reached a maximum, followed by a decrease with further decrease in OEGA. Effects of pH and NaCl concentration were also studied with P7 as an example. With increased pH in the aqueous solution (2.0 mg/mL) of P7 , the LCST increased and the fluorescence intensity decreased; With the increase in NaCl concentration, the LCST decreased, while no obverious change was detected for the fluorescence intensity. Furthermore, when the polymer concentration was increased, the LCST decreased, and the fluorescence intensity increased obviously. All the results indicate that the fluorescence emission was caused by aggregation of oxygen atoms in polymer segments. This study provides therefore a novel type of materials for potential applications in biomedical fields, and it is also of great significance for understanding the luminescence mechanism of PEG-based stimuli-responsive polymers.
Investigation of Chiral Recognition Mechanism of Polysaccharide Derivatives Based on Molecular Simulation
En-ting Deng, Wan-ying Bi, Bo Liu, Li-li Zhang, Jun Shen
六校 , doi: 10.11777/j.issn1000-3304.2019.19116
[Abstract](308) [FullText HTML](149) [PDF 975KB](11)
As one of the most powerful and popular chiral stationary phases (CSPs), phenylcarbamate derivatives of cellulose and amylose exhibit high chiral recognition ability and have realized efficent enantioseparation for almost 80% chiral compounds. To develop novel enantioseparation materials with high chiral recognition ability, it is of crucial importance to elucidate the chiral recognition mechanism for CSPs. Based on this, cellulose tris(phenylcarbamate) and amylose tris(phenylcarbamate) were synthesized by traditional esterification method in this study. The structures and degrees of substitution of the polysaccharide derivatives were characterized by 1H-NMR, implying that the obtained cellulose and amylose deivatives possessed regular higher order structures and almost complete substitution of phenylcarbamate pendants at three positions on the glucose units. The obtained polysaccharide derivatives were then coated on aminopropyl silica gel to prepare the chiral stationary phases (CSPs). The chiral recognition abilities of the derivatives were evaluated by the high performance liquid chromatography (HPLC) based on the separation of racemic 1-(9-anthryl)-2,2,2-trifluoroethanol (Rac-1). Then, based on the molecular mechanics and the molecular dynamics, molecular simulation of the higher order sturucture of polysaccharide derivatives were performed using Materials Studio software. The optimized conformation for the interaction between polysaccharide derivatives and enantiomers of Rac-1 was achieved by the molecular simulation according to the FTIR and XRD results. The molecular simulation results agreed well with the chiral recognition ability and elution order of enantiomers by HPLC. It indicated that the chiral recognition was significantly dependent on the synergistic interactions between polysaccharide derivatives and enantiomers of Rac-1 at the chiral grooves formed by the carbamate substituents and aromatic rings of the polysaccharide derivatives with different stabilities. This study may contribute to a better understanding for the chiral recognition mechanism of polymer-based CSPs.
Synthesis and Performance of a Double Network Self-healing Elastomer Based on Hydrogen Bonds and Diels-Alder Crosslinks
Yan Peng, Yu-jia Hou, Qiao-qiao Shen, Hui Wang, Gang Li, Guang-su Huang, Jin-rong Wu
六校 , doi: 10.11777/j.issn1000-3304.2019.19140
[Abstract](547) [FullText HTML](341) [PDF 1065KB](57)
Intrinsic self-healing elastomers, which can automatically heal themselves after damage without the addition of other reagents, have recently attracted increasing attention. However, a trade-off commonly exists between high mechanical properties and high self-healing efficiency, which is always the bottle-neck in advancing these high performance self-healing elastomers. To solve this problem, a high performance and high self-healing efficiency elastomer was developed in this work based on hydrogen bonds and Diles-Alder (DA) crosslinks. Firstly, a monomer (HM) functionalized with amido bond and carbamic acid ester for the generation of hydrogen bonds was synthesized by N-butyl isocyanate and N-(2-hydroxyethyl)acrylamide. Next, one-pot free-radical copolymerization of HM, butyl acrylate (BA), and furfuryl methacrylate (FMA) was carried out to afford a linear copolymer, which was only cross-linked with hydrogen bonds. Finally, bismaleimide (BMI) was used to crosslink the linear copolymer through DA reaction. A double network self-healing elastomer with two kinds of crosslinks, i.e. hydrogen bonds and DA bonds, was thus prepared. The heating-up and cooling down FTIR spectroscopy was used to characterize the hydrogen bonds, while the existence of DA bonds was proved by FTIR, DSC, and DMA techniques. When an external force was applied, the hydrogen bonds broke firstly to dissipate energy, which helped to increase the toughness by about 6.2 times, the tensile strength by about 12.3 times, and Young’s modulus of the elastomer by about 26 times. Meanwhile, DA crosslinks endowed the elastomer with certain elasticity and the capability of fast shape recovery. Moreover, thanks to the reversible ability of hydrogen bonds and DA crosslinks, the elastomer exhibited a high self-healing efficiency up to 98%.
Synthesis and Properties of a Novel Conjugated Acceptor Material for Organic Solar Cells Based on Indacenobis(dithieno[3,2-b:2′,3′-d]pyran)
Xin Ke, Lingxian Meng, Xiangjian Wan, Xin Zhang, Meijia Chang, Chenxi Li, Yongsheng Chen
四校 , doi: 10.11777/j.issn1000-3304.2019.19131
[Abstract](462) [FullText HTML](216) [PDF 925KB](35)
We designed and synthetized a new non fullerene acceptor with an A-D-A strucutre, named IDTO2HT-2F, based on indacenobis(dithieno[3,2-b:2′,3′-d]pyran) for organic solar cells. The dithieno[3,2-b:2′,3′-d]pyran will improve the electron-donating capability of the unit and lift the highest occupied molecular orbital (HOMO). Thus, the band gap decreases, making the maximum absorption peak red-shift. Theoretical calculation based on density functional theory (DFT) proved the feasibility of this molecular design. The molecule IDTO2HT-2F has a narrow bang gap of 1.30 eV with the solid absorption edge extended to 956 nm, which is complementary to that of the polymer PM6 film. The broad absorption of the active layer ensures the photovoltaic device to produce high photocurrent. With 0.5% DIO additive and thermal annealing at 120 °C for 10 min, the organic solar cell based on the acceptor IDTO2HT-2F and the polymer PM6 exhibits a power conversion efficiency (PCE) of 10.85% with a short circuit current density (Jsc) of 20.61 mA cm−2, an open-circuit voltage (Voc) of 0.86 V and a fill factor (FF) of 0.62. The results indicate that the strategy of introducing pyran into the molecular backbone is an effective way to tune the absorpion and energy level of the molecules, which is also a promisng method to design new non fullerene acceptors.
Reinforcing Styrene-Butadiene Rubber with Deformable Domains and Related Mechanisms
Li-jie Zhang, Jing Huang, Si-wu Wu, Zheng-hai Tang, Bao-chun Guo
六校 , doi: 10.11777/j.issn1000-3304.2019.19135
[Abstract](416) [FullText HTML](207) [PDF 1420KB](27)
In the present work, based on the coordination capability of nitrile groups in nitrile rubber (NBR) with metal ions, a novel type of rubber material with sacrificial domains was designed. Specifically, copper sulfate (CuSO4) and vulcanization package were introduced into styrene-butadiene rubber (SBR)/NBR blend by mechanical mixing and hot pressing. As a result, SBR with sulfur crosslinkings are formed as continous phases while the NBR mainly crosslinked by Cu(II)-nitrile coordination bonds are acted as dispersed phases, which are used as deformable domains to reinforce SBR. With the increasing concentration of coordination bonds in dispersed phase, both strength and modulus of the rubber improve rapidly. When 20 wt% NBR was introduced, the strength and modulus of SBR are increased by 2.6-fold and 3.2-fold, respectively. The significant reinforcing effect of this system is attributed to the strong yet deformable domains. The strong domains have hydrodynamic effect, which greatly improve the moduli of the samples. On the other hand, upon external stress, the loading can be rapidly transferred from SBR matrix to the domains owning to strong interfacial interactions, forcing the domains to develop high-elastic deformation prior to the rupture of SBR chains and dissipate mechanical energy, thus significantly enhancing the toughness of the rubber. This forced high-elastic deformation in domains can be recoverd through relaxation at a high temperature to fully restore the mechanical properties. Overall, this work provides a new way for the reinforcement of non-polar rubber through the design of deformable domains.
Systheisis of Vanadium Complexes Bearing Tridentate β-Ketoimine Ligands and Their Catalytic Capabilities towards Ethylene (Co)polymerization
Ling-pan Lu, Kai-ti Wang, Yi Liu, Jia-jun Wu
六校 , doi: 10.11777/j.issn1000-3304.2019.19128
[Abstract](549) [FullText HTML](275) [PDF 893KB](30)
Vanadium catalysts always show outstanding catalytic properties towards ethylene (co)polymeriztaion, while the high-valent vanadium species would be deactivated because of the generation of inactive or less active low-valent species at elevated temperature and/or in prolonged time. As proved, introducing of bulky groups into the ligands is benefit to improving the catalytic properties of vanadium complexes. Herein, in order to well control the oxidation state of vanadium species, a series of tridentate β-ketoimine type vanadium(III) complexes bearing cyclic skeleton {[(R)X(C6H4)N=CH(C6H5)C10H7O]VCl2(THF): 2a , R = CH3, X = S; 2b , R = CF3, X = S; 2c , R = Ph, X = S; 2d , R = tBu, X = S; 2e , R = Ph2, X = P; 2f , R = Ph, X = O}, were synthesized and characterized. Because of the constrained effects of the cyclic skeleton and the stabilizing effects of the bi-chelating ring, these synthesized catalysts showed high activities and improved stabilities in ethylene (co)polymerization. In the presences of Et2AlCl and ethyl trichloroacetate, catalysts 2a2f showed 8.16 − 19.9 kgpolymer/(mmolV·h), 7.68 − 26.9 kgpolymer/(mmolV·h) and 4.80 − 42.2 kgpolymer/(mmolV·h) of catalytic activities towards ethylene polymerization, ethylene/norbornene (NBE) copolymerization and ethylene/exo-1,4,4a,9,9a,10-hexahy-dro-9,10(1′,2′)-benzeno-1,4-methanoanthracene (HBM) copolymerization, respectively. All of the resultant polymers exhibited a unimodal distribution, indicating that these vanadium catalysts showed single-site catalytic behaviour, even at elevated temperatures (50 − 70 °C). Catalysts 2b , 2d , 2e and 2f showed "positive" comonomer effects in both ethylene/NBE copolymerization and ethylene/HBM copolymerization. Besides, 2a and 2c also exhibited positive comonomer effects in ethylene/HBM copolymerization. Cyclic olefin copolymers possessing high molecular weights (NBE: 43.1 − 66.4 kg/mol; HBM: 90.2 − 138 kg/mol) and high comonomer incorporations (NBE: 30.9 mol% − 42.1 mol%; HBM: 14.7 mol% − 25.0 mol%) were obtained facilely via direct copolymerization. The glass transition temperature is dominantly affected by the cyclic olefin incorporations and the steric hindrance of the cyclic olefin. Compared with the ethylene/NBE copolymers, the obtained ethylene/HBM copolymers showed much higher glass transition temperatures (NBE: 84 − 105 °C versus HBM: 173 − 188 °C).
Effect of High Temperature Annealing on Thermal Expansion Behavior of Poly(amide-imide) Films with Ultralow Coefficient of Thermal Expansion
Lan Bai, Lei Zhai, Min-hui He, Chang-ou Wang, Song Mo, Lin Fan
一校 , doi: 10.11777/j.issn1000-3304.2019.19099
[Abstract](584) [PDF 1137KB](28)
A kind of representative poly(amide-imide) (PAI) films derived from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) and amide-containing diamine i.e. N,N'-(1,4-phenylene)bis(4-aminobenzamide) (PABA) were prepared via thermal imidization, and then annealed at various high temperatures including 350, 375, 400 and 425 °C, respectively. With the increase of annealing temperature, the heat-resistance of PAI films were improved with higher Tg values, whereas their thermal decomposition stabilities were reduced to some extent especially when annealed above 400 °C. All of these PAI films exhibited ultralow thermal expansion with negative coefficient of thermal expansion (CTE) values from –6.87 ppm/°C to –3.84 ppm/°C even in a wide temperature range of 30 – 400 °C. It was noted that the CTE values of PAI films were increased to around zero as annealing temperature elevated. The annealing effect on aggregation structures and thermal expansion behavior was further investigated by birefringence (Δn), FTIR, WAXRD and WAXS. The birefringence of PAI films was extraordinarily larger than that of aromatic polyimide films, indicating that PAI molecular chains were more oriented in the in-plane direction. Their Δn values ranged from 0.2438 to 0.2621 as annealing temperature increased from 350 °C to 425 °C. The hydrogen bonding interactions were proved to be maintained even at high temperature as the main reason for the dimension stabilities of PAI films. It was also found that annealing at high temperature could contribute to the enhanced intermolecular interactions. In addition, the intermolecular chain distance of PAI films was observed to be reduced with the increasing temperature, suggesting that molecular chains were packed more densely. Furthermore, the interchain distance in the film thickness direction was more affected by annealing with large variation than that of in-plane direction. PAI-425 film showed significantly negative thermal expansion mainly because of its expanding out-of-plane interchain distance. Based on high temperature annealing, the relationship between thermal expansion behavior and aggregation structures of PAI films was established to be used for the regulation and control of thermal expansion. It provided a new strategy to prepare heat-resistant polymer films with ultralow CTE values by the structure design and high temperature annealing.
Modification of Microporous Polymer Membranes via Surface Co-deposition and the Separation Performances
Tan An, Hui Yu, Li-jun Xu, Zhi-kang Xu, Ling-shu Wan
四校 , doi: 10.11777/j.issn1000-3304.2019.19086
[Abstract](732) [FullText HTML](501) [PDF 1109KB](63)
Surface deposition systems such as dopamine and tannic acid have received great attention in recent years and have been widely applied in surface modification of polymer separation membranes. It is generally accepted that only polyphenols containing catechol structure can effectively form surface coatings. This paper reports a novel surface co-deposition systems based on ferulic acid and Cu2+. It should be noted that ferulic acid, a monophenol, contains only one phenolic hydroxyl group, without acatechol structure. Co-deposition coatings were prepared on various substrates, and the effects of composition and deposition time were investigated. Results indicate that the ferulic acid/Cu2+ system is able to form coating layer on most substrates. However, the coatings cannot be effectively formed on highly hydrophilic susbtrates such as silica, glass, and quartz. Microporous polypropylene membrane with surface coatings was prepared under optimal deposition conditions, and the surface structure and properties were characterized by field emission scanning electron microscopy (FE-SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), zeta potential analyzer, and water contact angle measurement. The modified membranes were applied to the separation of oil-in-water emulsions and dye adsorption. The results show that the modified membrane becomes hydrophilic and strongly negatively charged, while the surface porous structure changes little. The modified membranes can be used for the separation of various oil-in-water emulsions with high separation efficiency. It is also demonstrated that the membranes can be used repeatedly in the separation of emulsions. Furthermore, the coatings endow the membranes with strongly negatively charged surfaces, and hence the modified membranes show great potential in the adsorption of positively charged dyes. The results may introduce a novel monophenol-based system for surface deposition and greatly expand the types of surface deposition phenols.
Photo-thermal Storage and Release of an Azobenzene-grafted Polynorbornene Film
Lin-xia Fu, Yi-yu Feng, Wei Feng
四校 , doi: 10.11777/j.issn1000-3304.2019.19092
[Abstract](691) [FullText HTML](477) [PDF 1087KB](27)
The poor film-formation ability of azobenzene carbon thermal storage materials with graphene as templates limits their practical application due to the rigid structure of graphene sp2 hybridization. In this study, we addressed this issue by employing polynorbornene as the templelate given that polymers much outperform graphene in terms of film formation, flexibility, and self-supporting property. Herein, azobenzene attached with two methoxy and two carboxyl groups was firstly synthesized to regulate the photoisomerization and energy density. Next, polynorbornene (PNB) templates with various molecular weights were prepared by ring-opening metathesis polymerization (ROMP) with different molar ratios between monomer and catalyst. Azobenzene was then grafted onto the side chain of PNB through amidation reaction to afford azobenzene-grafted polynorbornenes with diverse grafting densities. Experimental results showed that with the increasing molecular weight of PNB template, the graft density of azobenzene rose first but subsequently fell. As for the film formation ability, PNB-Azo-500 with the highest graft density (36%) could hardly form an intact film, while PNB-Azo-900 exhibited the best film formation ability despite a slightly lower graft density (31%). Therefore, PNB-Azo-900 was involved in the following measurements. Tensile testing indicated that the PNB-Azo-900 film possessed good flexibility and self-supporting behavior by achieving a strain of 120% and a tensile strength of 21.5 MPa. Photoisomerization and energy density was characterized by UV-absorption spectroscopy and differential scanning calorimetry, respectively, which suggested that the film effectuated energy storage under 365 nm UV-light irradiation and the energy density reached 34 Wh/kg. The stored energy could be released as heat when the film was expoed to 550 nm green light or heat source stimulation, during which the highest temperature was 1.25 °C. Such excellent energy storage and light responsiveness endowed this PBN film with potential applications in the field of space thermal management.
Dynamic Numerical Simulation and Experiment Results of Oscillating Packing Injection Molding
Hao Yang, Wei-chen Zhou, Xue-qin Gao, Jun Lei, Zhong-ming Li
四校 , doi: 10.11777/j.issn1000-3304.2019.19111
[Abstract](635) [FullText HTML](504) [PDF 1151KB](18)
To realize the intelligent precision manufacturing of oscillating packing injection molding (OPIM), the whole process of OPIM was creatively simulated by computer-aided technology, Moldflow. In the process of simulation, the model was built as a dumbbell-shaped tensile spline and the complex dynamic fluctuating flow field caused by reciprocating piston motion in packing stage was initially emulated by the Dynamic feed system. According to complex changes of temperature, pressure and extra shear field, cross WLF model were selected as the constitutive laws for HDPE in this study. The melt flow distribution, variation of the melt temperature and shear field in sample were investigated in OPIM simulation, meanwhile the results were also compared with those of conventional injection molding (CIM) simulation. The results show that, in the OPIM process, HDPE melts could repeatedly pass through the cavity at lower viscosity by the strong reciprocating motion of pistons, creating the temperature gradient at the thickness direction and forming a strong shear field, thus inducing the molecular chains to straighten and further form the shish-kebab structures. Finally, The real morphology and structure of OPIM and CIM samples were characterized by 2D-WAXD、SEM. The results show a higher orientation and more shish-kebab structure in OPIM compared with those in CIM. Melt flow traces observed by microscopy confirmed the multiple melt flow under the action of pistons in cavity. The simulation results are in good agreement with our experiment results. Finally, this article provide the theoretical OPIM process window for high-performance sample processing and new simulation ideas for special injection moldings additional external force field.
Ring-opening Polymerization of Lactide by Bifunctional Organocatalyst at Ambient Conditions
Hai-qiang Li, Jing-yi Wang, Li Wu, Wei Liu, Rui-hua Cheng, Bo-ping Liu
三校 , doi: 10.11777/j.issn1000-3304.2019.19080
[Abstract](609) [FullText HTML](475) [PDF 809KB](11)
Ring-opening polymerization of lactide (LA) is one of the most important techniques to synthesize poly(lactic acid) (PLA). In this work, a series of organocatalysts have been prepared for both solution polymerization and bulk polymerization of LA at ambient conditions. Derived from the facile reactions between phthalimide and quaternaryammonium salt, these catalysts are inexpensive and stable in air. Tetraethylammonium 2-aminobenzoate (TEACB) (catalyst a) was first applied to polymerize LLA in toluene solvent, and a conversion of 42.7% was achieved after the reaction proceeded at 25 °C for 1 h. Orthogonal experiments suggested that the optimum condition was reaction temperature of 75 °C, reaction time of 4 h, and the molar ratio of lactide:catalyst a:alkoxide equal to 200:10:1, which afforded PLA product with molecular weight of 8.03 kg·mol–1, polydispersity index (PDI) of 1.53, and a high conversion of 88.5%. Next, bulk polymerization of LLA was carried out at different temperatures to explore the effects of initiator, alcohol salt, reaction time, and the molar ratio of lactide:catalyst:alkoxide. The catalytic activity of the catalysts depended largely on their chemical structures. Under the same reaction temperature, catalyst b with larger cation part led to a higher conversion; meanwhile, catalysts a and b with phenyl group in the anionic part were more active than catalyst c bearing an aliphatic group although the latter produced PLA with higher molecular weight and narrower molecular weight distribution. The catalysts developed in this study worked well in the absence of alkoxide, whilst alkoxide and alcohol could improve the performance of the catalyst system. LLA polymerizations could be conveniently performed under atmospheric conditions and increasing temperature resulted in PLA products with higher molecular weight and narrower molecular weight distribution. The conversion reached up to 95.7% after polymerization at 150 °C, in which the Mn and PDI of the PLA product equaled 2.57 kg·mol–1 and 1.24, respectively. DSC measurements indicated that PLAs obtained via varied methods displayed similar melting temperatures in the range of 130 – 134 °C. Further, cooperative dual activation of both the monomer and the initiator/chain-end could be confirmed based on MALDI-TOF-MS analyses. This novel catalyst system possesses specific monocomponent hetero-bifunction with H-bonding capability.
Effect of Sodium Dodecyl Sulfate on the Rheological Behavior of Poly(vinyl alcohol) Aqueous Solution
Xu Shaoshen, Du Miao , Song Yihu, Wu Ziliang, Zheng Qiang
最新录用 , doi: 10.11777/j.issn1000-3304.2019.19178
[Abstract](66) [PDF 0KB](1)
Rheological behaviors of poly(vinyl alcohol) (PVA) aqueous solution are influenced remarkably by the intermolecular hydrogen bond interaction in the semi-dilute solution region. Owing to the hydrogen bond network, 10 wt% PVA aqueous solution exhibits a high viscosity which limits its development of the solution processing method to some extent. Sodium dodecyl sulfate (SDS) as a surfactant can destroy the hydrogen bond interaction and thus play a certain viscosity-reducing role. Based on measuring the critical aggregation concentration (CAC) and critical micelle concentration of SDS in 10wt% PVA aqueous solution (CMCP), the steady and dynamic rheological behaviors of PVA-SDS aqueous solution were studied in detail. The concentrations of SDS (csur) influence the rheological behavior of PVA aqueous solution in different ways at various regions. ① csur < CAC, the apparent viscosity ( ) of the solution doesn’t change a lot as the csur changes. ② CAC < csur < CMCP, decreases as the csur increases. Particularly, reaches the minimum while csur = CMCP and a wider second platform is displayed in this area. ③ csur > CMCP, SDS form micelles that act as physical cross-linking points, and the dynamic storage modulus (G) of the composite solution also increases significantly. The changes in the hydrogen bond network of the PVA solution was indirectly characterized by the changes of the hydration number which were measured by Differential Scanning Calorimeter. After introducing SDS, the number of bound water (n) decreases due to the interaction between SDS and PVA. However, n almost keep constant when csur > CMCP. The viscous activation energy also shows similar changes. When csur is much larger, the micelles formed by SDS in water favor forming physical cross-linking network, which contribute more to the solution elasticity, leading to the increase of G being greater than that of dynamic loss modulus. Compared with the dilute solution, SDS has a greater viscosity reduction effect on the PVA semi-dilute solution.
Investigation of the Transformation Dynamics of Diblock Copolymers Assemblies in Reverse Solvent via Computer Simulation
Chun-yang Yu , Shan-long Li, Ke Li, Yong-feng Zhou
最新录用 , doi: 10.11777/j.issn1000-3304.2019.19173
[Abstract](151) [PDF 0KB](2)
In this paper, the transformation dynamics of diblock copolymers assemblies in reverse selective solvent were investigated using dissipative particle dynamics simulation. Simulation results show that after the change of solvent selectivity, the large spherical micelle was respectively transformed into the reverse spherical micelle in solution and the ring-like micelle at the interface. The simulation results were in agreement with the available experimental result. In addition, the simulation results also predicted that after the change of solvent selectivity, the ring-like micelle, the wormlike micelle and the vesicle were respectively transformed into the reverse ring-like micelle, the reverse ring-like micelle and multimicelle aggregate in solution, while they were respectively transformed into the branched wormlike micelle, the multilayer nanoparticle and the patch nanoparticle at the interface.
The Study of Cationic Copolymerization of Isobutylene and 4-(Chloromethyl)styrene
Ke Yang, Qiang Liu , Shuai Wen, Shu-xin Xu, Chen-qi Shi
最新录用 , doi: 10.11777/j.issn1000-3304.2019.19179
[Abstract](192) [PDF 1482KB](9)
Cationic copolymerization of isobutylene (IB) and chloromethylstyrene was investigated in n-hexane (Hex)/dichloromethane (CH2Cl2) (v/v=6/4) solvent with TiCl4, AlEt1.5Cl1.5, AlEt2Cl, AlCl3 as co-initiators and water or cumyl alcohol as initiators. The molecular weight, molecular weight distribution(MWD) and structure composition of the resulting copolymers were analyzed by gel permeation chromatography (GPC) and 1H-NMR spectroscopy. The reactivity ratios were determined by Kelen-Tüdős and Yezreielv-Brokhina-Roskin formula, and the copolymerization mechanism was proposed. Co-initiators with strong Lewis acidity, such as AlEtCl2, AlEt1.5Cl1.5 and AlCl3 were found can catalyze intermolecular alkylations resulting in the formation of gels while no gel formed with the relatively weaker TiCl4. The chloromethylstyrene with para-substituent, i.e., 4-(chloromethyl)styrene was found to have a low reactivity during the copolymerization with IB (rIB = 4.67, rp-CMS = 0.70) while the ortho-isomer exhibited no activity. The chemical structure of resulting copolymers indicated that 4-(Chloromethyl)styrene cannot initiate the polymerization of IB which might because of its low initiation rate compared to the highly active cumyl group. However, the benzyl chloride group in the formed copolymer chain can slowly initiate polymerization of IB and 4-(chloromethyl)styrene, forming branched structures. The content of 4-(chloromethyl)styrene increased with increasing molecular weight and monomer conversion. Systematic research on the branched structure, rheological properties and other physical properties of the resulting copolymers is in progress.
High-performance thin film composite forward osmosis membrane with polydopamine/polyethyleneimine (PDA/PEI) co-deposition interlayer
Shao-Fei Wang, Yuan Yu, Qing-Yun Wu
最新录用 , doi: 10.11777/j.issn1000-3304.2019.19193
[Abstract](0) [PDF 0KB](0)
A novel thin film composite (TFC) forward osmosis (FO) membrane was prepared by using a polydopamine/ polyethyleneimine (PDA/PEI) co-deposition interlayer on cellulose triacetate (CTA) porous substrate followed by an interfacial polymerization. The surface structures and properties of CTA substrates and TFC membranes were systematically investigated by FTIR/ATR spectroscopy, scanning electron microscopy, atom electron microscopy, solute rejection method, and water contact angle test. The results show that the surface of CTA substrate deposited by PDA/PEI interlayer becomes smooth and has narrow surface pore size distribution as well as small surface pore size of 30.0  4.1 nm. Meanwhile, the polyamide film formed on the PDA/PEI co-deposition interlayer presents homogeneous leaf like structure and excellent hydrophilicity. Therefore, TFC FO membrane with PDA/PEI co-deposition interlayer achieves an improved water flux of 7.1  2.3 L/m2h, raising by 57.6% compared with nascent TFC FO membrane; a low reverse salt flux of 1.4  0.1 g/m2h, and a small specific salt flux of 0.2  0.06 g/L, decreasing by 83.9% and 90.6%, respectively. It means that PDA/PEI co-deposition interlayer facilitates to improve both water permeability and selectivity of TFC FO membrane.
Enhanced Energy Storage Performance of Polyimide-based Nanocomposites by Introducing Two-dimensional Nanosheets
Fu-rong Li, Jianying Zhao , Hai-quan Guo , Lian-xun Gao
最新录用 , doi: 10.11777/j.issn1000-3304.2019.19164
[Abstract](168) [PDF 2682KB](17)
Demands to improve the energy storage density of polymer dielectric materials have spurred the development of polymers with enhanced permittivity and improved dielectric breakdown. Introducing high permittivity fillers can effectively improve the polymer permittivity, but also easy to cause the reduction of breakdown strength, which affected the improvement of the energy storage density of polymer materials. In this paper, the polyimide-based nanocomposite films were fabricated through the incoporation of the high permittivity barium titanate (BT) nanoparticles and two-dimensional nanosheets exfoliatred from hydrotalcite (HT) as fillers via the in-situ polymerization. The permittivity of PI/BT films gradually increased with the increase of the content of BT nanoparticles. However, the breakdown strength decreased significantly with the increase of BT content. Therefore, the energy storage density of PI/BT composite films showed a significant decrease. However, with a small amount of two-dimensional nanosheets of hydrotalcite adding to the PI/BT composite films, the breakdown strength of the composites showed a obvious increase trend. The breakdown strength of the PI/BT film conntaining 30% BT was increased by 32.8% when only 1% two-dimensional nanosheets were added. The feature that two-dimensional nanosheets could improve the breakdown strength of PI/BT composites were identical for different contents of BT. Hence,the addition of the two-dimensional nanosheets could effectively improve the breakdown strength of PI/BT composite film, and then enhance the energy storage density. This is due to the fact that two-dimensional nanosheets can effectively improve the dispersion of high content nanoparticles in the polymer matrix, thus improving the properties of composites related to the dispersion of nanoparticles. Experimental results showed that the introducing of two different morphology fillers could improve simultaneously the permittivity and breakdown strength of PI/BT/HT composite films. Compared to adding only 20% BT to the polymide matrix, when 20% BT and 1% HT were added togrther, the energy storage density of PI/BT/HT nanocomposite films could reach 2.58 J/cm3, increasing by 14.6%. This method of simultaneously adding two different morphology fillers such as nano particles and two-dimensional nanosheets into the polymer matrix was expected to be applied in more fields of nanocomposite materials, especially with high content of nano particles.
Effect of Hydrogen on Copolymerization between Dichlorosilane-Functionalized Nonconjugated α,ω-Diolefin and Propylene
Xue-min Yin, Ya-wei Qin, Li-yang Zhang, Shuai Ma, Jin-Yong Dong
最新录用 , doi: 10.11777/j.issn1000-3304.2019.19187
[Abstract](43) [PDF 0KB](7)
Dichlorosilane functionalized nonconjugated α,ω-diolefin and propylene copolymers, catalytically prepared by heterogeneous Ziegler-Natta catalyst, could trigger dehydration condensation reaction between different polypropylene chains to form long-chain branched structure in the presence of water. Hydrogen is usually used as a chain transfer agent in olefin polymerization to regulate the molecular weight of polymer. So it is an important scientific topic whether hydrogen affects the insertion of the di(5-hexenyl)dichlorosilane in the propylene polymerization. In this paper, the polypropylene microstructure was analysed by varying with hydrogen content when the amount of di(5-hexenyl)dichlorosilane was fixed. The 1H NMR results showed that the pendant double bonds in the polymer chain decreased which illustrated that hydrogen inhibits the insertion of di(5-hexenyl)dichlorosilane in propylene polymerization. The higher the hydrogen content, the lower insertion of di(5-hexenyl)dichlorosilane in the polymer chain. That is, the long-branched chain density in polymer is reduced. And there is no gel in the polymers in the presence of hydrogen. The rheological test results also verified that the long-branched chain density decreases with increasing the hydrogen content.
Atomic Force Microscopy Studies of Polymer Crystallization in Thin Film: Understanding the Formation Mechanism and Tuning the Properties
Bin Zhang
最新录用 , doi: 10.11777/j.issn1000-3304.2019.19185
[Abstract](51) [PDF 0KB](1)
Over the past decade, besides fundamental concepts, single-crystal engineering of functional polymers and its applications have attracted increasing attention. With the advances of multiparametric and multifunctional characterization, atomic force microscopy (AFM) not only can image the surface topography of polymer crystals in nanoscale while simultaneously mapping the physical properties, like the electrical and thermal properties, but also provides a unique way of linking molecular structures, crystallization conditions and post-treatment to properties. Furthermore, the nanoscale control afforded by scanning probe lithography (SPL) has prompted the development of a regulation of the polymer aggregation structures and surface patterns in thin films. To explicitly probe the mechanism of polymer crystallization, single layer lamella and few layer lamellae in thin films as a model system, combined with AFM can provide information on polymer nucleation and growth with high spatial and temporal resolution. On the other hand, to promote a better understanding of the nature of heterogeneities of metastable state within the lamellae, lamellar thickening/melting and self-seeding, the effects of annealing temperature and time on lamellar thickness of metastable folded-chain crystals have been investigated in polymer thin films.
Sustainable Polymers Based on Natural Terpenes
Jie Hao, Yuxia Gao, Hourui Chen, Jun Hu , Yong Ju
最新录用 , doi: 10.11777/j.issn1000-3304.2019.19180
[Abstract](103) [PDF 2760KB](21)
The development of sustainable polymers has been an important research topic to meet the need of nonpetroleum-based materials and to reduce the dependence on fossil fuel. Terpenes, a kind of natural products with extensive supply sources, has multiple reactive sites and abundant functionalities. It can not only simplify the synthesis of sustainable polymers, but also endow them with unique stereochemical structures, good biological activity and biocompatibility, thus broadening their applications in surface coating, biological medicine and tissue engineering. This paper reviews the progress of natural terpene-tailored sustainable polymers in recent decades, including molecular design, performance characteristic, and potential applications.

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2019, 50(11).
[Abstract](151) [PDF 2447KB](20)
Janus Polymerization: A Novel Approach towards Topology Design
Huan Qiu, Yao Li, Tian-wen Bai, Jun Ling
2019, 50(11): 1133-1145. doi: 10.11777/j.issn1000-3304.2019.19150
[Abstract](935) [FullText HTML](371) [PDF 2527KB](93)
Janus polymerization combines cationic and anionic polymerizations at two ends of a single propagating chain involving a living/controlled chain-growth polymerization and a self-triggered stepwise polycondensation, which provides a facile way to synthesize novel polymers with sophisticated topologies in one step directly from monomers. Di-/Multi-block copolymers, branch polymers, mikto-arm star copolymers and cylindrical polymer brushes are synthesized using rare earth triflates catalysts assisted by various epoxy initiators owing to their specific position at the middle of the chain. This work reviews recent progress on Janus polymerization in our group. Specifically, the characteristic of rare earth metal catalysts and mechanism of Janus polymerization are discussed in detail where tripedal crows are employed to illustrate the mechanism. New methodologies for the construction of topological polymers are introduced, together with the unique and prominent properties, such as thermoplastic properties, self-assembly and self-healing behaviors and the corresponding applications in self-sealing films for plants and electrostatic spinning. A new Janus system is put forward which affords a facile synthetic method for functional polyesters by incorporating a modifiable monomer 3,3-bis(chloromethyl)oxacyclobutane. Finally, the development of Janus polymerization including new catalytic systems and monomers is also prospected. The concept of Janus polymerization makes significant breakthroughs into traditional cognitions about incompatible cationic and anionic polymerization mechanisms in one system which motivates the power in the catalysis and synthesis of polymer chemistry.
Cascade Polymerization
Ying-feng Tu
2019, 50(11): 1146-1155. doi: 10.11777/j.issn1000-3304.2019.19094
[Abstract](915) [FullText HTML](469) [PDF 2200KB](92)
Cascade polymerization, or domino polymerization, is a polymerization process involving two or more consecutive polymerizations under the same reaction condition, in which the subsequent polymerizations result as a consequence of the functional polymer intermediates formed in the previous polymerization step, i.e., two or more polymerizations proceed cascade in an in situ one feeding step, one pot system. As the separation and purification of intermediate polymers are not needed, cascade polymerization has the characteristics of " green” and high efficiency, which is especially important in the synthesis of block copolymers. This review introduces the concept of cascade polymerization, with the focus on the cascade polycondensation-coupling ring-opening polymerization (PROP) method developed by our research group, as well as the kinetics, thermodynamics and the application of PROP in the synthesis of polyesters and copolyesters. By the combination of chain-growth and step-growth polymerization together in one system, PROP has the merits of fast polymerization speed, easy to handle with mild polymerization conditions, controlled rigid to soft segments weight ratio, and can be used for the synthesis of multiblock copolymers which are hard to be synthesized by traditional polymerization techniques. These multiblock copolyesters have potential applications in elastomers and energy storage materials.
Acid-activatable Polymeric Drug Delivery Systems for Cancer Therapy
Jing Gao, Wei-qi Wang, Hai-jun Yu
2019, 50(11): 1156-1166. doi: 10.11777/j.issn1000-3304.2019.19133
[Abstract](804) [FullText HTML](339) [PDF 3746KB](99)
The polymeric drug delivery systems (DDS) have showed promising potential for improving cancer therapy, which can lengthen the blood circulation and minimize the adverse effect of chemotherapeutics. Despite promising, the therapeutic performance of polymeric-based DDS is affected by a series of physiological barriers, including limited tumor accumulation, restricted tumor penetration, insufficient cellular uptake, and slow drug release inside the tumor cells. It has been well-investigated that there is an acidic microenvironment inside the solid tumors due to the abnormal glucose metabolism of tumor cells. Moreover, the subcellular organelles including endosome and lysosome display much lower acidic pH than that of cytosol. The extracellular and intracellular acidic microenvironments have thus been exploited as both a trigger and target for tumor-targeted drug delivery. In this review article, we summarized our recent advances in developing acid-responsive polymeric DDS by taking the advantage of the acidic microenvironment of tumor tissue and tumor cells. We particularly highlighted the acid-responsive chemical bonds and components employed for constructing the acid-activatable DDS. These acid-activatable nanovectors have been exploited for combating the physiological barriers by surface charge conversion, nanostructure dissociation, and ligand presentation. We also provided a perspective regarding of the challenges and opportunities about clinical translation of the stimuli-activatable DDS.
Synthesis of Oxidation Responsive Vesicles with Different Block Sequences via RAFT Polymerization-induced Self-assembly
Jin-wen Zheng, Xiao Wang, Ze-sheng An
2019, 50(11): 1167-1176. doi: 10.11777/j.issn1000-3304.2019.19070
[Abstract](873) [FullText HTML](564) [PDF 1090KB](50)
Block copolymer (BCP) nanoparticles with three different block sequences, PDMA-PNAT-PDAAM (M-N-D), PDMA-PDAAM-PNAT (M-D-N) and PDMA-P(NAT-co-DAAM) (M-[N-co-D]), are prepared via polymerization-induced self-assembly (PISA). Soluble N-acryloyloxy thiomorpholine (NAT) and diacetone acrylamide (DAAM) are used as monomers to form insoluble core blocks in water, while PDMA35 bearing a trithiocarbonate is utilized as stabilizer and macromolecular chain transfer agent (macro-CTA) to render a RAFT control. Specifically, M-[N-co-D] nano-objects are synthesized via direct RAFT dispersion copolymerization of NAT and DAAM at 70 °C employing PDMA35 macro-CTA. To produce M-N-D and M-D-N triblock copolymers, PDMA-PNAT (M-N) and PDMA-PDAAM (M-D) nano-objects are prepared via RAFT dispersion PISA syntheses of NAT and DAAM respectively utilizing PDMA35 macro-CTA and then used for seeded dispersion polymerization of DAAM and NAT respectively without intermediate postpolymerization purification. The thioether moiety in NAT can be oxidized by reactive oxygen species (ROS) into a hydrophilic sulfoxide. Therefore, in the precense of hydrogen peroxide (H2O2), oxidation-responsive morphological degradation of these nano-objects occurs due to the increasing hydrophilicity of NAT units. Given the poor control over polymerization of NAT in pure water, 1,4-dioxane is used as a cosolvent to the PNAT block. So the PISA syntheses are conducted in water/1,4-dioxane (9/1, V/V) mixture to achieve a good control over the molecular weight and narrow distribution. 1H-NMR spectra indicate that quantitative monomer conversions (> 99%) are achieved within 5 h. Differential scanning calorimeter (DLS) and transmission electron microscopy (TEM) are used to characterize final morphologies of PISA-generated nano-objects and morphological evolution of nano-objects in the presence of H2O2 (10 mol/L). These aqueous sequence-controlled PISA formulations are expected to provide responsive nanoparticles with tunable kinetics due to the response-dependent morphological transitions, which may be potentially used as carriers for drug delivery and controlled release.
Synthesis of Long Chain-branched Polypropylene Based on Dichlorosilane-functionalized Nonconjugated α,ω-Diolefin and Ziegler-Natta Catalyst
Hang-sheng Zhou, Kang Li, Ya-wei Qin, Jin-yong Dong
2019, 50(11): 1177-1186. doi: 10.11777/j.issn1000-3304.2019.19078
[Abstract](666) [FullText HTML](482) [PDF 1705KB](46)
This study discusses a new strategy for synthesis of long chain-branched polypropylene (LCB-PP) with Ziegler-Natta catalysts, which, on the basis of conventional nonconjugated α,ω-diolefin/propylene copolymerization incapable of affording LCB, utilizes a dichlorosilane-functionalized α,ω-diolefin instead to carry out the copolymerization. Such a copolymerization with Ziegler-Natta catalysts will give PP bearing pending dichlorosilane functional groups, and it will undergo facile interchain condensations, leading to long chain-branched formation under methanol treatment and water vapor treatment. A MgCl2/TiCl4 catalyst containing a diether-type internal electron donor, 9,9-bis(methoxymethyl)fluorine (BMMF), was employed to catalyze di(5-hexenyl)dichlorosilane/propylene copolymerization in slurry conditions. It was found that di(5-hexenyl)dichlorosilane neither did harm to catalyst activity, nor changed the chain transfer/chain termination reaction of the original propylene polymerization. Incorporations of the mono-polymerized di(5-hexenyl)dichlorosilane were found to be between 0.02 mol% and 0.1 mol%. After the copolymerization completed, the obtained copolymers were treated with methanol or water vapor, respectively. Both the treatments could effectively transform the polymer chains-pending dichlorosilane groups into siloxane groups. The condensation degrees were distributed, which were centralized between 2 and 3 with methanol treatment. Water vapor treatment showed higher efficiency for dichlorosilane condensation than methanol treatment did. It could be found that water-treated samples exhibited systematically higher degrees of long chain-branched than their methanol-treated counterparts did with multiple evidences. Gel permeation chromatography measurement showed that the molecular weights of the copolymerized samples treated by both water vapor and methanol were improved, and the copolymers treated by water vapor in the Mark-Houwink equation curve were more deviated from the linear polypropylene than those of methanol treatment. The linear viscoelasticity of copolymers with different di(5-hexenyl)dichlorosilane concentrations after water vapor treatment and methanol treatment was investigated by means of small amplitude oscillatory shear (SAOS) to verify the existence of long chain-branched structure. According to extensional rheometry measurement, the strain hardening phenomena of the copolymers treated with water vapor were more obvious than those treated with methanol.
Synthesis and Properties of Carbazole-functionalized Isotactic Polypropylenes
Rui-ning Shang, Huan Gao, Yu-lian Li, Bin Wang, Zhe Ma, Li Pan, Yue-sheng Li
2019, 50(11): 1187-1195. doi: 10.11777/j.issn1000-3304.2019.19081
[Abstract](663) [FullText HTML](472) [PDF 1350KB](20)
A series of novel amino-functionalized isotactic polypropylenes with high molecular weight and satisfying functional comonomer incorporation were prepared by direct copolymerization of propylene and α-olefins carrying carbazole functional groups. The homogeneous non-metallocene catalyst system consisting of dimethyl(pyridylamido)Hf(IV) complex, [Ph3C][B(C6F5)4], and AliBu3 showed good tolerance to carbazole groups and promoted the copolymerization of propylene with 11-carbazole-1-undecene effectively under mild reaction conditions, in which very high catalytic activity (up to 4.08 × 106 gpolymer molCat.−1 h−1) was achieved. The functional copolymers obtained possessed high molecular weight (up to 7.02 × 105) and tacticity ([mmmm] > 99%), as well as decent incorporation of carbazole functional groups (up to 13.5 mol%). Besides, DSC and TGA results verified the excellent thermostability of most copolymer products by giving decomposition temperatures around 450 °C as well as high melting points. Representative physical properties such as hydrophilicity, mechanical performance, and fluorescent characteristics of these iPPs functionalized by carbazole groups have also been explored. The increased incorporation of 11-carbazole-1-undecene monomer could reduce the water contact angle gradually and thus make significant improvement in surface properties; the copolymers became hydrophilic when comonomer incorporation exceeded 4.1 mol%. In terms of the mechanical properties, elongation at break of the copolymer barely increased at low incorporation (1.2 mol%), and the material still showed typical attributes of rigidity and brittleness. As more 11-carbazole-1-undecene monomer was incorporated (> 6.2 mol%), toughness of the materials was dramatically enhanced yet their stiffness was inevitably sacrificed. In addition, the introduction of carbazole group endowed the copolymers with unique fluorescent characteristics—they could emit purple fluorescence under 365 nm UV light in both solution and film states, thereby making this kind of functional polypropylene materials valuable and promising for the extensive applications in optoelectronic devices.
Synthesis and Properties of Hydrophilic Poly(propylene carbonate) under UV Irradiation
Ling-ling Yu, Rui-hua Cheng, Yu-tao Tong, Bo-ping Liu
2019, 50(11): 1196-1201. doi: 10.11777/j.issn1000-3304.2019.19053
[Abstract](730) [FullText HTML](525) [PDF 944KB](62)
To improve the hydrophilic properties of poly(propylene carbonate) (PPC), hydroxyl-functionalized PPC (PPC-OH) were prepared by two steps. First, PPC containing o-nitrobenzyl (ONB) protecting groups (PPC-ONB) were synthesized by terpolymerization reactions of 2-{[(2-nitrophenyl)methoxy]-methyl}oxirane (monomer a ), propylene oxide (PO), and CO2 over SalenCo(III)Cl/bis(triphenylphosphine)iminium chloride (PPNCl) catalyst system. 1H-NMR result showed that the PPC-ONB was a random copolymer with monomer a randomly inserted. Then PPC-OH were obtained with the removal of o-nitrobenzyl (ONB) protecting groups under ultraviolet (UV) irradiation. PPC-ONB were synthesized with various feed ratios of the monomer a and different reaction time. Based on the analysis of 1H-NMR, 13C-NMR, gel permeation chromatography (GPC), and differential scanning calorimeter (DSC), SalenCo(III)Cl catalyst performed high reactivity and high selectivity (> 94%). The polycarbonate exhibited excellent regioselectivity and perfect alternating copolymerization of CO2 and PO with the carbonate linkages up to 98%, and the head-to-tail linkage (HT) up to 99%. With the increase of the feed ratios of the monomer a , the polymer ratio of the monomer a increased to 19.4% without sacrificing the reactive activity, while the molecular weight (Mn) decreased slightly owing to the better reactivity of monomer a . The glass transition temperatures (Tg) were in the range of 35.7 − 38.9 °C. The kinetics of deprotection by UV irradiation proved that the ONB protecting groups could be carried out efficiently within minutes. And the characterization of polymer by 1H-NMR, Fourier transform infrared spectrometer (FTIR) and GPC showed that the ONB protecting groups were removed and the ―OH was observed. Meanwhile, no degradation of polymer backbone occurred. The contact angle (CA) measurement of PPC-ONB and PPC-OH displayed a difference in hydrophilia. The hydrophilia of PPC-OH has been greatly improved compared with PPC-ONB due to the increase in polarity, and the CA of PPC-OH decreased from 78.3° to 58.6° when the molar ratio of ―OH increased to 19.4%.
Study on the Construction of 3D-BN Network in Epoxy Resin by Introducing Foam Skeleton
Rong Yan, Ling Zhang, Chun-zhong Li
2019, 50(11): 1202-1210. doi: 10.11777/j.issn1000-3304.2019.19064
[Abstract](689) [FullText HTML](488) [PDF 1303KB](75)
It is a traditional method to improve the thermal conductivity of matrix by adding fillers. However, it is a great challenge to construct a dense heat conduction network in composite material. The current researches on building thermal conductive network is to combine different fillers through structure design for achieving high thermal conductivity with the lowest possible filler content. Due to the electrical insulation requirements of electronic equipment, hexagonal boron nitride (h-BN) has been extensively studied as an inorganic thermal conductive filler. It has a layer structure that shows a relatively high TC of 300 W·m–1·K–1 in the h-BN planar direction. In this study, the foam was introduced into the epoxy resin as a skeleton, and thermal conductive network was constructed by immersing the BN/E51 mixture into the foam. By comparing the hot deformation behavior of two kinds of foams with different structures and compositions: polyurethane foam (PF) and nano-melamine (melamine) foam (MF), epoxy resin-based composites with high thermal conductivity were obtained by hot press curing under the right compression ratio. PF has a large single arm size and good elastic deformation ability, but it is easy to become a barrier between BN, which is bad for forming thermal conductive path after compression. However, MF has a small single arm size and can be broken into four needle-like scaffold structures after compression. The needle-like scaffold structure promotes the good dispersion of BN, and finally forms a thermal path of BN throughout the material, which plays a key role in improving the thermal conductivity of the composite. As a result, MF-BN/E51 showed an excellent thermal conductivity of 3.88 W·m–1·K–1 at 41 wt% BN load when the degree of hot pressing was 90%. It provides a new way for the composites to achieve a higher thermal conductivity with a less filler load.
Accelerating the Design and Synthesis of Heat-resistant Silicon-containing Arylacetylene Resins by a Material Genome Approach
Ming Chu, Jun-li Zhu, Li-quan Wang, Jia-ping Lin, Lei Du, Chun-hua Cai
2019, 50(11): 1211-1219. doi: 10.11777/j.issn1000-3304.2019.19076
[Abstract](822) [FullText HTML](688) [PDF 1189KB](36)
We developped a material genome approach to accelerate the design and synthesis of novel heat-resistant silicon-containing arylacetylene resins. The material genome approach is based on the consideration that silicon-containing arylacetylene resins can be regard as a combination of silane and diyne units which can be defined as genes used for combination screening. The approach presented here contains two steps. In the first step, various kinds of diynes were collected from the chemical database as candidate structures; the bond dissociation energy (BDE) reflecting heat resistance of resins was calculated; the candidate structures were preliminarily screened with the criteria of BDE; and finally 16 diynes with high BDE were obtained. In the second step, LUMO-HOMO and 50% decomposition temperature (Td50) were calculated by density functional theory and molecular connection index method, respectively; and the optimized gene was obtained out of 16 candidate structures. The screened resin is poly(diphenylsilylene-ethynylene-naphthalene-ethynylene) (abbreviated as PSNP) containing the gene of 2,7-diethynylnaphthalene. To verify the screened results, we first synthsized the PSNP by Sonogashira coupling of dichlorodiphenylsilane and 2,7-diethynylnaphthalene. The molecular structure of PSNP resin was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR). The curing process of PSNP resin was studied by differential scanning calorimetry (DSC). The results show that the curing peak temperature (Tpeak) of PSNP and the enthalpy of exothermic reaction are 212 °C and 173.8 J/g, respectively, which are lower than those of traditional poly(silylene-acetylenearyleneacetylene) resin (PSA). The cured PSNP resin exhibits excellent heat-resistance, where the 5% decomposition temperature (Td5) of the cured PSNP resin is 561 °C. The properties of the resin are consistent with the theoretical design results, which confirms the validity of material genome method for structural screening of new silicon-containing arylacetylene resins.
A Simulation Study of Enhancing the Compatibility in Block Copolymer AB/Homopolymer C Blends by Solvents
Zhi-yao Liu, Zheng Wang, Yu-hua Yin, Run Jiang, Bao-hui Li
2019, 50(11): 1220-1228. doi: 10.11777/j.issn1000-3304.2019.19072
[Abstract](690) [FullText HTML](498) [PDF 1275KB](41)
The phase behavior of diblock copolymer AB/homopolymer C blends in solution was studied by simulated annealing method. The study was focused on the compatibilization between the homopolymer and the copolymer with repulsive interactions due to the addition of solvent. We investigated the amount of solvent (characterized by the concentration of the polymer segments Φ), the volume fraction fc of the homopolymer C, the ratio of homopolymer chain length to the copolymer chain length X, the repulsion between C and A or B segments, εAC and εBC, and the attraction between solvent and C on the phase behavior of the blending system. We built phase diagrams in the space of Φ and fc at different X. Studies have shown that when X is less than 0.5, and the values of εAC and εBC are not very large, the addition of solvent strongly selective to A and C segments can improve the compatibility of the system. In solution, lamellae, gyroids, cylinders in layers, core-shell cylinders and cylindrical structures are formed. Moreover, the structure of cylinders in layers has not been observed in the neat diblock copolymer system. C-segments are distributed at the interfaces between A/B domains at high Φ region, while they are inside the A domain at low Φ region. Short homopolymer chains are easily compatible with diblock copolymers. Macroscopic phase separation has taken place in long homopolymer chains even with a small amount of homopolymer added. Moreover, increasing the values of εAC and εBC will reduce the compatibility of the system. The transformation between different phases and that from microphase separation to macrophase separation are the results of the competition between the energy and entropy of the system. The macrophase separation in the solution system is different from that in the melt system. Some C-segments are at the interface of AB domains to reduce the contact between A and B segments in the solution system, while all C-segments are separated from the AB domains in the melts.
Migration of Ring Polymers in Poiseuille Flow and Comparison with Linear Polymers
Zhen-yue Yang, Wen-duo Chen, Li-jun Liu, Ji-zhong Chen
2019, 50(11): 1229-1238. doi: 10.11777/j.issn1000-3304.2019.19074
[Abstract](562) [FullText HTML](367) [PDF 1296KB](19)
The dynamical and conformational properties of individual ring polymers with different chain lengths are investigated in Poiseuille flow through a tube using a hybrid mesoscale hydrodynamic simulation method, and migration behaviors are compared with those of linear chains. As the flow strength is increased, the ring chains migrate towards the centerline of the tube when the hydrodynamic interactions are included, but towards the tube wall when the hydrodynamic interactions are switched off. By analyzing the radial center-of-mass distribution function and the width of the distribution function of the ring chains, our studies reveal that the migration towards the centerline of the tube should be attributed to the hydrodynamic interactions rather than to the shear gradient in the Poiseuille flow. With the increase of flow intensity, the ring chains stretched more along the flow direction and shrunk smaller along the radial direction, independent of the location of their center-of-mass across the tube. When the hydrodynamic interactions are switched off, the extension along the flow direction and the shrinkage along the radial direction of the ring polymers are more pronounced than those with the hydrodynamic interactions. For a given flow strength, the longer the ring chain is, the eaiser it is to concentrate around the center of the tube due to the stronger hydrodynamic interactions between the chain and the tube wall, and the resulting distribution structure transits from the platform to the bimodal, and finally to the single-peaked with increasing chain length. By comparing the center-of-mass distributions and the structural properties between the ring and linear chains with the same chain length or the equilibrium radius of gyration, our simulation results show that the linear chains exhibit a more stretched conformation along the flow direction than the ring polymer chains, leading to the outward migration with a lower number density in the tube center.
  • Editor: Xi Zhang

    Establishment Time: 1957

    Adminidrated by: Chinese Academy of Sciences

    Sponsors by: ICCAS
     Chinese Chemical Society


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