最新刊期
卷 52 ， 期 11 ， 2021
- 摘要：The construction of supramolecular chiral materials from achiral building-units has always been a challenging topic in the field of chiral research. It can not only avoid tedious synthesis steps and the use of expensive chiral raw materials, but also provide the understanding of the origin of chirality in chiral materials. Traditionally, it is non-covalent bonds that often act as the "bridge" between the building blocks and chiral superstructure. However, the chiral ordered structures formed by these weak interactions are often easily destroyed by outer stimulus, such as light, heat or solvent, which is completely irreversible without the pre-chiral source. Recently, Wei Zhang and co-workers at Soochow University reported the permanent memory of chirality in achiral polymer system, by combining chiral induction and covalent cross-linking strategy. Interestingly, the stored chiral information in cross-linked structure can trigger the perfect chiral self-recovery (CSR) behaviors after being destroyed by UV light, heat and solvent. This results will pave a new way for producing novel chiroptical materials with reversible chirality from achiral sources.关键词：Chiral induction;Chiral storage;Chiral self-recovery;Supramolecular chirality
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发布时间：2022-07-08 - 摘要：Surface and interface are the important windows for us to learn the unique physical chemistry of polymer materials. Recently, Professor Biao Zuo and his collaborators used atomic force microscope to observe the creep relaxation of surface wrinkle at the edge of ionic liquid droplet on the smooth surface of polystyrene. They found that in the low temperature region nearby body glass transition temperature of polystyrene, the creep relaxation could not reproduce the time-temperature superposition law as observed in the high temperature region. Since surface polymers hold relatively high mobility, there exists a mobility gradient from the surface to the body of polystyrene. They performed molecular dynamics simulations to demonstrate that the body glassy state brings constraint to the surface polymers, and it expands the modulus plateau of the rubbery states of surface polymers in the low temperature region. Leaving away from the surface, the glassy part of surface polymers plays the role of physical crosslinking, restricts the mobility of surface polymers, and thus enhances their rubbery behaviors in the low temperature region. This work challenges the current hypothesis of entanglement network, causing the rubbery state of bulk amorphous polymers. Once linear polymers make the partial frozen of the glassy states in their bulk amorphous phase for physical cross-linking, they could attain the unique rubbery states, distinguished from small molecules.关键词：Surface and interface;Atomic force microscope;Rubbery state;Glassy state
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发布时间：2022-07-08
- 摘要：The ceramizable polymers are a group of special functional polymers which can transform from organic cross-linked network to inorganic ceramics during pyrolysis or service under high temperature. This article reviews the latest research on ceramicizable polymers and their derived functional ceramics used under extreme and special environment and aerospace field. According to main elements contained in ceramicizable polymers, the design and synthesis of boron, zirconium, hafnium, iron-containing ceramic polymers are introduced in detail. The stoichiometric ratio, cross-linkable feature and linear, slightly cross-linked and hyperbranched topologies of ceramicizable polymers are key factors to the properties of pyrolyzed ceramics, including ceramic yield, mechanical property, high-temperature resistant and anti-oxidation performances. Due to their ceramicizable feature during pyrolysis or service, self-healing, and flame retardancy under high temperature or arc, the advanced ceramicizable polymers show remarkable application in high-temperature resistant and anti-oxidation ceramics, high-temperature adhesives, arc breakdown resistance and flame retardant coatings mainly used in extreme conditions. Then the new developments in the multifunctionalization of ceramicizable polymers such as electromagnetic wave absorbing materials and electromagnetic interference shielding materials are presented. The introduction of transition metal into ceramicizable polymer is highly effective to tune dielectric and magnetic properties of their derived ceramics. The excellent electromagnetic wave absorption at 885 ℃ with a low minimum reflection coefficient and a wide effective absorption bandwidth was achieved on iron-containing siliconboron carbonitride ceramics derived from the cross-linked network of hyperbranched polyborosilazane and 1,1'-bis(dimethylvinylsilyl)ferrocene. In addition, the perspective and further development of integration and intersection of ceramizable polymers are proposed, including but not limited to additive manufacturing, high-temperature self-healing and long-life composites, as well as metamaterials with potential in electromagnetic wave absorbing material at low frequency of 0.5-2 GHz.关键词：Ceramizable polymer;Ceramic precursor;High-temperature electromagnetic wave absorbing material;Electromagnetic interference shielding material
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发布时间：2022-07-08 - 摘要：Developing a new system of material chemistry is an important molecular foundation for the design and preparation of function-oriented materials. However, precisely controlling the design and synthesis processes of function-oriented materials is still a grand challenge in the field of material chemistry. In terms of polymer science, a major scientific issue is how to manipulate polymers as precisely as "genes" in living systems to control the precise synthesis of polymeric monomers, the precise transmission of sequence information, and the functionalized customization of polymeric materials, which is named as "gene-like" construction of functional polymeric materials. Desoxyribonucleic acid (DNA) with its intrinsic genetic property has exhibited a variety of unique advantages for the "gene-like" construction of polymeric materials. As the central genetic matter of life system, DNA is a bioactive macromolecule with the capacity of encoding the genetic sequence information, which is favourable to the construction of function-oriented materials with living characteristics. This review summarizes the "gene-like" construction of DNA functional materials, mainly from our research group, focusing on the construction strategies of two DNA functional materials including branched DNA and DNA hydrogels. The construction strategies of branched DNA functional materials mainly include target-triggered polymerization, enzymatic extension and hybrid coupling, and the construction strategies of DNA hydrogels are categorized as module assembly, enzymatic amplification, enzymatic elongation, chain hybridization reaction and chemical crosslinking. The molecular assembly principles and functional regulation mechanisms were further disscussed. DNA molecule shows the unique advantages in the "gene-like" construction of functional materials, mainly including the precise arrangement of polymeric monomers, the controllable design and assembly of structure, the precise transmission of sequence information and function customization. Particularly, the sequence information of DNA endows the specific biological functions of DNA functional materials by regulating the order of polymeric monomers. Finally, we exemplify the typical cases of DNA functional materials based on "structure-function-application" research route, focusing on protein production, 3D cell culture, cell interfacial engineering, disease treatment and other biomedical fields. It is expected that the flourishing development of DNA functional materials will open a new avenue and provide a feasible paradigm for the "gene-like" construction of functional polymeric materials.关键词：DNA functional polymer;DNA hydrogel;Branched DNA;DNA nanotechnology;"Gene-like" construction of materials
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发布时间：2022-07-08
Feature Articles
- 摘要：In recent years, with the development of donors and acceptors in active layer, the efficiency of single-junction organic solar cells (OSCs) has now exceeded 18%, which is regarded as one of the third-generation photovoltaics with broad application prospects. However, the relatively low stability of the devices remains the biggest bottleneck, which hinders the industrial application of the OSCs. And the simultaneous improvement of the device efficiency and stability still faces a big challenge. One of the effective strategies is to introduce various types of additives into the OSCs. As one of the most potential additives in OSCs, insulating polymers are capable of forming ternary hybrid structures with donors and acceptors, or have good self-assembly properties, which improve the PCE effectively. Meanwhile, due to their excellent stability or physical properties, insulating polymers are conducive to maintaining the morphology of the active layer and isolating oxygen and water, which enhance the stability of devices and greatly promote the development of OSCs. The challenges of device efficiency and stability that OSCs faces are summarized. The recent research progress of a series of insulating polymers as active layer additives in the applications of OSCs is reviewed. The methods for improving the efficiency and stability of devices in terms of the formation of ternary blend structures between the insulating polymers and active layer materials, as well as the formation of interface structures by self-assembly and migration are systematically discussed. Finally, the potential and application prospects of insulating polymers as additives in photovoltaic devices are indicated.关键词：Organic solar cells;Insulating polymers;Self-assembly;Glass transition temperature;Interface layer
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发布时间：2022-07-08
Reviews
- 摘要：High-capacity Si/C anodes face the huge volume change during Li insertion/extraction process, which consequently leads to the pulverization of the silicon and eventually capacity fading and poor cycle life of lithium-ion batteries. To tackle this issue, new binder materials is extensively explored to improve the cycle life by effectively alleviating the huge volume change, and thus improving the cycling life. In this work, a new cross-linkable aqueous composite binder based on branched polyethyleneimine and polyacrylamide (BPEI-PAM) for Si/C anodes is reported. TGA, DSC, FTIR measurements are performed to characterize the crosslinking reaction of BPEI and PAM and their thermal properties. The electrochemical performances of the Si anodes with BPEI-PAM new binder are investigated and compared with the conventional aqueous binder of carboxymethyl cellulose/styrene butadiene rubber (CMC/SBR). By using the optimized BPEI-PAM binder (1:6 in molar ratio), the Si/C electrode exhibits the higher peel strength of 0.82 N/cm as compared with 0.32 N/cm for CMC/SBR. Even at a high loading of 3.0 mg/cm2, the Si/C electrode with BPEI-PAM can still maintain 81.3% capacity retention after 200 cycles, better than 76.1% for the electrode with CMC/SBR. This improved electrochemical performances can be attributed to the higher adhesion property of BPEI-PAM binder after crosslinking during the process of Si/C electrodes.关键词：Lithium-ion battery;Si/C anode;Aqueous binder
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发布时间：2022-07-08 - 摘要：As a new generation of olefin polymerization catalyst, pyridylamido hafnium catalysts have unique ligand-modified activation mechanism and high isoselectivity for α-olefins polymerization. In this study, polymerizations of 4-methyl-1-pentene (4MP) and 1-hexene (Hex) catalyzed by classic pyridylamido hafnium catalyst were investigated, especially for the copolymerizations of 4MP and Hex. The pyridylamido hafnium catalyst showed high activity toward homo- and copolymerizations of 4MP and Hex. Isoselective homopolymerization of 4MP afforded narrowly polydispersed poly(4-methyl-1-pentene) (PMP) with high melting temperature up to 239 ℃, while homopolymerization of Hex produced amorphous poly(1-hexene) with a bimodal distribution. Random copolymers of 4MP and Hex with different compositions were synthesized by adjusting the feed ratio of monomers. With decreasing feeding ratio of 4MP/Hex, monomer conversion and copolymerizataion activity increased because the hex-inserted hafnium active species was more active than the 4MP-inserted hafnium active species. Besides, decreasing feeding ratio of 4MP/Hex also led to a decrease in molecular weight and melting temperature of copolymer but caused a broadening in molecular weight distribution. 1H- and 13C-NMR spectrocopies clearly proved the resultant random copolymers were highly isotactic ([mmmm]>99%). The analysis results of differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXD) of polymers showed that the insertion of Hex unit into PMP changed its melting temperature and crystallization property.关键词：Hafnium catalysts;4-Methyl-1-pentene;Copolymerization;Isotacticity
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发布时间：2022-07-08 - 摘要：High density polyethylene (HDPE) prepared by Ziegler-Natta catalyst does not contain long chain branching structure, which results in limits in its processing and applications. How to introduce long chain branching structure into HDPE prepared by Ziegler-Natta catalyst is one of the long-term challenges in olefin polymerization research. This study discusses a new synthesis of long-chain-branched high-density polyethylene(LCB-HDPE) based on Ziegler-Natta catalysis. ω-Alkenylmethyldichlorosilane was used as LCB reagent, which is introduced into ethylene polymerization to generate PE chains containing pendant reactive dichlorosilane groups by ethylene/5-hexenylmethyldichlorosilane copolymerization. Followed by treating the polymer powders with water, the neigboring polymer chains-grafted dichlorosilane groups are hydrolyzed and H-type LCB structure is formed by hydrolytic condensation. The results indicate that the combination of Ziegler-Natta catalysts and the ω‑alkenylmethyldichlorosilane copolymerization-hydrolysis chemistry resulted in successful preparation of LCB-HDPE with LCB density up to 0.15/1000C and hardly affected catalyst activity. The LCB-HDPEs have significant rheological properties responses. Their melt elasticity, zero-shear viscosity, melt strenght and strain-hardening effect all increase/intensify with the increase of LCB densities. Meanwhile, the LCB-HDPEs maintain high crystallization properties. With melting temperatures and crystallization temperatures being largely equivalent to those of linear PE, their crystallinities increased to a noticeable degree. It is expected that the new LCB-HDPEs with simultaneously high crystallinity and high melt strength will have good applications in the fields where the melt strength is highly required.关键词：5-Hexenylmethyldichlorosilane;Ethylene polymerization;Ziegler-Natta catalyst;Long-chain-branched polyethylene
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发布时间：2022-07-08 - 摘要：In this contribution, a “one-pot, two-step” approach was adopted to synthesize high-density polyethylene-block-isotactic polypropylene diblock copolymers via the coordination chain transfer polymerization. Dibenzylbis(salicylaldimine) zirconium/methylaluminoxane catalyst system could promote the coordination chain transfer polymerization of ethylene to yield bis(polyvinyl)zinc in the presence of diethyl zinc as the chain transfer agent. The bis(polyvinyl)zinc served as a chain transfer agent in the subsequent propylene polymerization, which was promoted by dimethyl[(amido)(naphthyl)pyridine] hafnium catalyst and gave a series of polyethylene-block-polypropylene copolymers. Molecular weight and molecular weight distribution, thermal properties and microstructure of the newly obtained block copolymers were clearly characterized by high temperature gel chromatography (GPC), differential scanning calorimetry (DSC), high temperature nuclear magnetic (NMR), etc. Finally, the diblock copolymers (10 wt%) was also blended with commercially available PE and iPP (70/30) to improve their compatibility. As SEM analysis revealed, dispersed phase particle size was significantly reduced upon the addition of the block polymer, and the interfacial bonding of the two phases could be obviously improved. This research not only provides new polymerization method for the synthesis of block copolymer, but also affords good PE/PP compatibilizers. The newly resultant PE-b-iPP block copolymers are expected to play a promising role in the recycling of the waste PE and PP plastic and the sustainable development.关键词：Coordination chain transfer polymerization;Bis(polyvinyl)zinc;Block copolymer;Compatibilizer
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发布时间：2022-07-08 - 摘要：The polypropylene/multi-walled carbon nanotubes (PP/MWCNTs) composite replicas with densely distributed nanohairs on their surfaces were rapidly prepared by injection-compression molding (ICM). It was demonstrated that the nanohairs endowed the replica surface with superhydrophobicity (a contact angle of 159.2°) and extremely low adhesion (a roll angle of less than 3°). Both the MWCNTs and nanohairs effectively reduced the reflectance on the replica surface (the average reflectivity was only 5.5% in the wavelength range of 300 - 800 nm) and promoted the replica to absorb sunlight (its average surface temperature was raised from 0 ℃ to 77.4 ℃ under 1 sun illumination for 300 s). Both the wetting state and efficient photothermal conversion endowed the replica with higher anti-icing and deicing/defrosting abilities. The freezing time of water droplet on the replica surface was prolonged significantly and the ice droplet was quickly removed under 1 sun illumination. During photothermal defrosting, the frost fragments curled into spherical melting droplets and melting droplets spontaneously slid on the replica surface. The surface coverage fraction of the melting droplets was only 7.5% at the end of fully defrosting. The results demonstrate that it is feasible to rapidly fabricate superhydrophobic polymer (nano)composite surfaces with higher passive anti-icing and photothermal deicing/defrosting abilities.关键词：Polypropylene/multi-walled carbon nanotubes nanocomposite;Injection-compression molding;Nanohairs;Photothermal;Deicing/defrosting
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发布时间：2022-07-08 - 摘要：Natural aging of polyolefins is the comprehensive result of multiple environmental factors, such as UV irradiation, temperature, humidity and oxygen. But till now natural aging result is difficult to be simulated by accelerated aging. In this study, a lab-developed system was used to realize an in situ multi-factor aging evaluation under adjustable UV irradiance, temperature, humidity and oxygen concentration. Gaseous degradation products (CO2 is typical) were detected and the formation rate of CO2 was exploited to evaluate the stability. High formation rate (high aging speed) corresponds to low stability. By this system, single-factor aging speed equation of aging speeds of polypropylene (PP) and polyethylene (PE) versus UV irradiance, or temperature, or humidity, or oxygen concentration were established. Furthermore, multi-factor aging speed kinetics models of PP and PE were established and the parameters were fitted. Based on the multi-factor aging kinetics equations, the yearly aging speed “maps” in China and monthly aging speed “spectra” in some cities of PP and PE were drawn. This information is instructive to practical outdoor applications of PP and PE. The sensitivity of PP and PE to environmental factors was analyzed. It was found that PP is much more sensitive to irradiance and humidity than PE, a little more sensitive to oxygen concentration than PE, but is less sensitive to temperature than PE. This strategy can also be used for other polymer materials to establish their own multi-factor aging kinetics equations.关键词：Polypropylene;Polyethylene;Multi-factor coupling;Aging kinetics
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发布时间：2022-07-08
Articles
- 摘要：Atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) has been used widely in the investigation of molecular forces because of its friendly user interface (e.g., easy to operate and can work in liquid, air and high vacuum phase) and worldwide commercialization. This review is aimed to introduce the principle and protocol of AFM-based SMFS including the setup, the working principle, typical curves, the choice of AFM tip and substrate, immobilization of samples, manipulation of the device, empirical criteria for single-molecule stretching and data analysis. Recent progresses on the application of AFM-based SMFS in the characterization of synthetic polymers and biopolymers were reviewed. For synthetic polymers, the effects of primary chemical compositions, side groups, tacticity and solvents on the single chain elasticities were discussed. The applications of AFM-SMFS in disclosing the structure of unknown molecule, polymer-interface interactions and polymer interactions in polymer assemblies (e.g., polymer single crystal) were introduced. In addition, the nature of mechanochemical reactions and characterization of supramolecular polymers were realized via this technic. For biopolymers, the effects of base-pair number, the force-loading mode (unzipping or shearing) on the stability of short double-stranded DNA (dsDNA) were reviewed. According to this knowledge, the single-molecule cut-and-paste based DNA assembly was then discussed. The typical force fingerprints of long dsDNA, proteins and polysaccharides as well as the force-fingerprint-based investigation of molecular interactions were illustrated. Finally, the application of AFM-SMFS in revealing the intermolecular interactions and the mechanism of virus disassembly as well as the antivirus mechanism of tannin in tobacco mosaic virus were reviewed.Therefore, AFM-based SMFS is essential for revealing the relationship between the conformation/composition of polymer chains and micro/macro-mechanical properties of polymer materials as well as correlating the molecular structure/interaction of biopolymers with their biofunctions.关键词：Atomic force microscopy-based single-molecule force spectroscopy;Synthetic polymers;Biopolymers
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发布时间：2022-07-08
Reviews (Special Topic: Techniques of Polymer Characterization)
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