最新刊期
卷 ， 期 12 ， 2016
- 摘要：Organic porous polymer (OPP) materials are a class of multi-dimensional porous network materials, which are built via the strong covalent bonds linkage of various organic building blocks with different geometries and topologies, and recently become a new rising research field in porous material sciences.OPPs can be generally divided into two categories based on their degree of long-range order, including amorphous (e.g. CMPs, HCPs, PIMs, PAFs, etc.) and crystalline (e.g. COFs, CTFs) catalogues.Owning to their advantages of light-weight, large specific surface area, superior inherent porosity, excellent stability, pre-designable and precise tuneable structures and functions, OPPs have received increasing attention and research interests for their tremendous potential applications in gas storage/separation, heterogeneous catalysis, photoelectric conversion, chemical-and bio-sensing, energy storage and conversion, etc. We have developed a series of two dimensional (2D) and three dimensional (3D) functional organic porous network materials with excellent optoelectronic, or catalytic properties constructed by one or multiple organic conjugated building blocks owning specific functions, through self-polycondensation or copolymerization based on the so-called "bottom-up" strategy.In this article, we summarized recent examples reported by our group for the construction of multi-functional conjugated porous polymers of weaving organic conjugated functional molecules based on the bottom-up strategy, with a focus on the introduction of their structural features and exploration of their potential applications in photoelectric conversion and heterogeneous catalysis.Typical examples, of CMPs and COFs served as photodetectors, solid-state emitters, energy storage/conversion materials, and heterogeneous oxidation catalysts, were accordingly discussed.Some personal perspectives and challenges on the development of organic porous polymers were proposed in the last part of this article.Different from their counterparts (e.g. MOFs and zeolites), OPPs own a much more bright future in photovoltaics and energy storage materials (e.g. supercapacitors and batteries) due to their superior stabilities and facile chemical post-functionalization.关键词：2D polymers;Porous polymers;Covalent organic frameworks;Photo-electronic-and magnetic functional materials;Heterogeneous catalysis
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发布时间：2021-03-22 - 摘要：Synthetic polymeric chemistry is one of the basic parts of polymer science, and highly efficient polymerization reactions are essential for the synthesis of high performance polymeric materials, for which the development of new synthetic methods for the emerging polymer science is of great importance.Bergman cyclization is a chemical process during which highly reactive aryl diradicals are formed from enediyne precursors.Bergman cyclization has shown strong impacts on a number of application fields including pharmaceutics, synthetic chemistry and material science.The diradicals intermediates stemmed from enediynes can cause DNA cleavage under physiological conditions, leading to the strong cytotoxicity of many naturally occurred enediyne antibiotics.Meanwhile, the diradicals intermediates can quickly couple with each other to construct polyarylenes, providing a novel method to synthesize this kind of conjugated polymers thanks to the advantages of facile operation, high efficiency, tailored structure and catalyst-free feature.Moreover, the conjugated polymers generated through Bergman cyclization show many remarkable properties, such as excellent thermal stability, good solubility and processability, which enables these polymers to be further manufactured into carbon-rich materials.In this article, a brief overview of the trajectory of Bergman cyclization in polymer science was introduced, followed by the introduction of the research advances mainly from our group in developing polymerization methods with Bergman cyclization, taking advantages of its catalyst-free, by-product-free features and in situ polymerization mechanism to synthesize new polymeric materials with various structures and morphology.These synthetic strategies include fabrication of rod-like polymers with polyester, dendrimer and chiral imide side chains, functionalization of carbon nanomaterials by surface-grafting conjugated polymers, formation of nanoparticles by intramolecular collapse of single polymer chains, construction of carbon nanomembranes on the external and internal surface of inorganic nanomaterials.These polymers with novel structural features were further used in a variety of fields like energy transformation, energy storage, catalyst support, and fluorescent detection.At the end of this article, an outlook of the future development of Bergman cyclization in medicinal chemistry and especially in polymer science is presented.关键词：Bergman cyclization;In situ polymerization;Polymer nanocomposites materials;Two dimensional polymers;Controlled synthesis of polymers
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发布时间：2021-03-22 - 摘要：Polyoxometalates (POMs), as a kind of inorganic cluster containing various transition metal elements, have attracted tremendous attentions due to its defined structures and diverse properties in optical, electric, magnetic, catalytic, and biological areas. The combination of POMs and block copolymers could not only improve the processability of POMs which is one of the common obstacles for most inorganic materials in practical applications, but also endow the hybrids with new properties, i.e. stimuli-responsive properties. POMs/block copolymer hybrid materials could be built up through noncovalent and covalent interactions. Compared with covalent interactions, diverse noncovalent interactions could endow hybrid materials with flexibility and responsiveness. The individual properties of POMs and block copolymers could be integrated and magnified through noncovalent interactions. In this review, the fabrication strategy of POMs/block copolymers hybrid materials through noncovalent interactions and especially the stimuli-responsive hybrid systems were introduced. In the first part of this review, the fabrication strategies of the hybrids through noncovalent interactions were comprehensively summarized. Electrostatic attractions as a dominative driving force have been widely used to establish hybrids based on the anionic POMs and the cationic block polymers in a straightforward way. Besides, covalent bonds and H-bonding interactions were also introduced into hybrids establishment based on the electrostatic interactions, further enriching the fabrication strategies and assembling behaviors. Diverse morphologies, like micelles, vesicles, fibers, tubes, rings, films, and gels, would be observed through various strategies. In the second part, the stimuli-responsive behaviors of POMs/block copolymers based hybrids were introduced. The changes of physicochemical properties of both block copolymers and POMs could be triggered by extra stimuli such as pH, gas, and electrical signals. The stimuli-responsiveness of block copolymer and/or POMs could not only alter the assembling behaviors of hybrids, but also create new functions which could be accomplished by none of the individual component. By integrating the advantages of block copolymers and POMs, this kind of hybrid materials has a promising future in realms of biomaterials, sensors, and smart materials.关键词：Polyoxometalate;Block copolymer;Hybrid;Stimuli-responsive
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发布时间：2021-03-22
Feature Articles
- 摘要：Poly (vinylpyrrolidone) (PVP) immobilized zinc halides, ZnX2(PVP) (X=Cl, Br and I), were prepared by reaction of ZnX2 with PVP and used as catalyst for one-pot melt transesterification of diphenyl carbonate (DPC) with diols to synthesize high-molecular-weight aliphatic polycarbonates (APCs).The relationship of structure and catalytic performance was investigated using elemental analysis, FTIR, TGA and XPS for these catalysts.It was found that Zn2+ can be chelated with PVP through two ways, i.e. (a) Zn2+ ions anchored to oxygen and nitrogen in one amide moiety; (b) Zn2+ ions coordinated to two carbonyl oxygen atoms to from two neighboring amide ligands.The Mw, yield and PDI of obtained PBC were influenced by the halogen anions because the interaction of halogen anions, PVP and Zn2+ could obviously affect the varieties of Lewis acidity and steric hindrance of Zn2+.Lewis acidity was found to be dominant for the polymerization rate at lower temperature, and increasing steric hindrance seemed to give a positive effect on the improvement of yield.Polymerization and its reverse reaction, decomposition processes, were both promoted by increasing Lewis acidity, and the side reactions would be restrained by increasing the steric hindrance of Zn2+.Therefore, the increase of Mw and yield for ZnBr2(PVP) compared with ZnBr2 and ZnCl2 at a high temperature was mainly resulted from the conflicting factors of Lewis acidity and steric hindrance of Zn2+ compensated each other, thus generating the best activity for ZnBr2(PVP) at higher temperature, where the highest Mw of 1.59×105 with yield of 84.5% was obtained under suitable reaction conditions.The main reasons for ZnBr2(PVP) catalyst displaying the higher yield and Mw than other plain zinc halide catalysts should be ascribed to the presence of the interaction between ZnBr2 and PVP, which provided this melt transesterification reaction with appropriate Lewis acidity as well as the steric hindrance.In addition, the electronic density of O atom in diols also played a crucial role in this reaction.关键词：Zinc halide;Poly (vinylpyrrolidone);Aliphatic polycarbonate;Biphenyl carbonate;Melt transesterification
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发布时间：2021-03-22 - 摘要：Syndiospecific homopolymerization of styrene derivatives with different substitution groups such as methyl, methylsilylene, double bond group and their syndiospecific copolymerization with ethylene by half-sandwich scandium complex (C5Me4SiMe3) Sc (CH2C6H4NMe2-o)2 in combination with one equivalent of[Ph3C]B (C6F5)4] were examined.In the homopolymerization, the scandium complex displayed high activity (106 g polymer (mol Sc)-1 h-1) and gave highly syndiotactic poly (p-methylstyrene) and highly syndiotactic poly (p-vinylphenyldimethylsilane) with controlled molecular weight (Mn=1.3×105-5.7×105) and narrow molecular weight distribution (Mw/Mn=1.48-2.11).In the homopolymerizations of divinylbenzene and p-vinylphenyl-1-butene, cross-linking reaction took place at different extent and the corresponding cross-linking or mico-crosslinking polymers with bimodal GPC profile were obtained.The half-sandwich scandium complex showed no activity in the polymerization of α-methylstyrene under the same conditions, possibly owing to the steric bulkiness of the monomer.More important, by use of this scandium complex, copolymerization of p-methylstyrene and p-vinylphenyldimethylsilane with ethylene under 1.01×105 Pa of ethylene has also been achieved with the copolymerization activity reaching up to 106 g polymer (mol Sc)-1 h-1 at room temperature.The copolymerization afforded a novel family of functional polyolefins with syndiotactic poly (styrene derivatives) blocks, controlled molecular weight and narrow molecular weight distribution.Composition, structure and thermal properties of the novel copolymers were studied using 1H-NMR, 13C-NMR and DSC analysis.These functional copolymers were featured by multi-blocks, including syndiotactic poly (p-methylstyrene) blocks, syndiotactic poly (p-vinylphenyldimethylsilane) blocks, polyethylene blocks and ethylene-styrene derivatives sequences.Styrene derivatives content (8 mol%-55 mol%) and molecular weight (Mn=3×104-1.6×105) of the copolymers were easily controlled by changing the feed ratio of styrene derivatives and catalyst.The copolymers obtained from p-methylstyrene/ethylene and p-vinylphenyldimethylsilane/ethylene with different composition exhibited a melting temperature at about 127℃, originated from polyethylene blocks.When p-methylstyrene content in the p-methylstyrene/ethylene copolymers was more than 55 mol%, the copolymers showed a glass transition temperature at 98℃, originated from syndiotactic poly (p-methylstyrene) blocks.关键词：Scandium;p-Methylstyrene;p-Vinylphenyldimethylsilane;Ethylene;Copolymerization
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发布时间：2021-03-22 - 摘要：Cellulose derivatives (SP-HPC) containing different contents of spiropyran moieties were synthesized by esterification reaction between hydroxypropyl cellulose (HPC) and 3-(3', 3'-dimethyl-6-nitrospiro[chromene-2, 2'-indolin]-1'-yl) propranoic acid (SPCOOH), using dicyclohexylcarbodiimide/4-dimethylamiopryidine (DCC/DMAP) as catalyst in tetrahydrofuran at room temperature.The structure of SP-HPC was characterized by 1H-NMR, FTIR.SP-HPC with different degree of substitution (DSSP) of SP group was obtained.Meanwhile, DSSP of SP-HPC was increased and reached a maximum of 1.08 when the mass ratio of SPCOOH/HPC was increased to 1.5.SP-HPC was dissolved in THF and this solution showed rapid reversible UV light stimuli response.The colorless solution of SP-HPC in THF changed to modena after UV irradiation, and a peak at 570 nm in UV-Vis spectrum appeared and reached its maximum at 15 min, because loop-locked SP groups was transferred to ring-opening conjugated merocyanine (MC).After the solution being placed in dark for the same time, it turned back to colorless due to the transfer of MC to SP.It was more interesting that SP-HPC was able to self-assemble to form stable spherical micelles in water with hydrophobic SP moiety collapsed in the micelles due to the amphiphilic property of SP-HPC, which were characterized by DLS and TEM.Larger was the DSSP of SP-HPC, bigger was the size of the micelles.The average hydrodynamic radius (Rh) of SP-HPC micelles was 140 nm when DSSP was 0.3, and this radius was increased to 299 nm when DSSP increased to 1.08.The reason for this was that the enhanced hydrophobic property with higher DSSP led to more SP-HPC macromolecule aggregation.The micelles also showed stimuli response to UV light.Under UV irradiation, MC groups transferred from spiropyran type stacked more tightly, resulting in shrinkage of the micelles.SP-HPC films showed reversibly photochromic properties, but the transfer from MC to SP in dark was slower than that from SP to MC by up-taking energy.关键词：Spiropyran;Hydroxypropyl cellulose;Esterification;Micelles;Photochromism *
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发布时间：2021-03-22 - 摘要：A ratiometric fluorescent probe for Hg2+ ions in aqueous media based on organic/inorganic hybrid nanoparticles was prepared.Amphiphilic diblock copolymer, poly (3-(trimethoxysilyl) propyl methacrylate-co-NBDAE)-b-poly (N-isopropylacrylamide-co-RhBHA), abbreviated as P (MPS-co-NBDAE)-b-P (NIPAM-co-RhBHA), was firstly synthesized via consecutive reversible addition-fragmentation chain transfer (RAFT) polymerization of MPS and NIPAM monomer together with NBDAE and RhBHA respectively, where NBDAE and RhBHA were 7-nitro-2, 1, 3-benzoxadiazole (NBDAE)-based acrylic derivative monomer and Hg2+-reactive rhodamine B (RhB)-based acrylamide derivative monomer, respectively.Upon exposure to aqueous media, the amphiphilic diblock copolymer of P (MPS-co-NBDAE)-b-P (NIPAM-co-RhBHA) underwent self-assembly to form spherical nanoparticles with NBD-labeled PMPS cores and thermos-responsive PNIPAM coronas co-labeled with RhBHA moieties.Then a sol-to-gel process was conducted via addition of trimethylamine (TEA) into the micellar solution as the catalyst, resulting in core-crosslinked organic/inorganic hybrid nanoparticels.In the absence of Hg2+ ions, the micellar solution of the hybrid nanoparticles was solely green emissive under UV irradiation, which was originated from the NBD moieties trapped in the crosslinked PMPS micellar cores.However, upon addition of Hg2+ ions into the aqueous solution, Hg2+ induced ring-opening of the lactam ring in RhBHA moieties and thus generated RhB residues capable of fluorescence emission.Due to the fluorescence resonance energy transfer (FRET) between NBD and RhB moieties that were located in the micellar cores and coronas and acted as FRET donors and acceptors respectively, when the aqueous micellar solution was exposed to UV irradiation, a drastically green-to-orange emission transition was facilely discerned by both naked eye and fluorescence spectrometry, thus allowing for probing Hg2+ ions in a ratiometric manner.Moreover, because of the thermos-responsiveness of PNIPAM blocks, the collapse of PNIPAM coronas was induced by increasing the solution temperature, and the spatial distance between NBD and RhB moieties was therefore shortened, leading to an enhanced probing sensitivity.As a result, the organic/inorganic nanoparticle-based fluorescent probe could be employed as a highly selective ratiometric fluorescent sensor for Hg2+ in aqueous solution.关键词：Hybrid nanoparticles;Fluorescence resonance energy transfer;Ratiometric;Fluorescent sensor;Hg2+ ions;Thermo-responsiveness
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发布时间：2021-03-22 - 摘要：Using hydroxypropyl terminated polydimethylsiloxane (HP-PDMS), isophorone diisocyanate and 2, 2-bis (hydroxymethyl) butyric acid as starting materials, silicone-polyurethane copolymer (Si-PU) latexes with particle diameter of about 50 nm were prepared via step-by-step feeding process followed by phase inversion technique in the absence of surfactant.Influences of the HP-PDMS content on the phase structure and the properties of the Si-PU latex films were investigated, and the difference between Si-PU and polyether polyurethane (E-PU) was emphasized.It was found that the content of PDMS in Si-PU could reach up to 65 wt%.Results of DSC analysis showed that, in comparison with the E-PU latex film, the Si-PU latex films exhibited well phase separation.Strong hydrogen bonding in Si-PU hard segments was confirmed by FTIR, which promoted the micro-phase separation in the latex films.On the contrary, strong hydrogen bonding existed in between the soft and hard segments in E-PU, which led to phase mixing and prevented the formation of phase separation structure.The Si-PU latex films were characterized by AFM tapping mode and the formation of sea-island phase separation was observed, and this kind of phase separation structure in the Si-PU latex films was rarely reported in the literature, in which the amorphous PDMS-enriched domains constituted the dispersed phases.With the increase in HP-PDMS content, the degree of phase separation in the Si-PU latex films increased as well, which led to the decrease of elastic modulus from 400.0 MPa to 32.2 MPa with an increase in elongation at break and in the flexibility.The initial decomposition temperature of the Si-PU latex films was at about 244℃, which was 18℃ lower than that of the E-PU latex film due to the low degree of hydrogen bonding between the soft and the hard segments, whereas the thermal stability of Si-PU at high temperature zone was much better than E-PU.Compare to the E-PU latex film, a low water adsorption rate under 11% and a high contact angle above 94° indicated excellent water resistance of the Si-PU latex films.关键词：Polyurethane;Silicone;Phase separation;Structure-property relationship *
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发布时间：2021-03-22 - 摘要：Based on polyhexamethylene guanidine phosphate (PHMGP)/ammonium polyphosphate (APP)/PHMGP/potassium alginate (PA)-carbon nanotube (CNT), a unique quadlayer (QL) hybrid organic-inorganic film is built via layer-by-layer self-assembly to protect cotton fabric from fire.Fourier Transform Infrared and Ultraviolet-visible Spectroscopy indicate that PHMGP, APP, PA and CNT respectively grow linearly during the assembly process.Insulation resistance measurement reveals that, because of the cross-linked CNT network formed in assembly coating on fiber, 10 QL coating makes a decrease by orders of magnitude, from 1.8×1010 Ω·cm to 9.1×104 Ω·cm, in the electrical resistivity of cotton fabric, which implies that the electrical conductivity of cotton has been improved greatly.Characterizations of thermal and combustion behaviors for all fabrics show that QL coating performs an excellent flame retardant effect on cotton, which is stronger than that of PHMGP/APP bilayer coating (P/A).P/A coating has stronger catalytic effect on the thermal decomposition of the cotton with respect to the QL coating of equal weight.This can be confirmed by the lower T-5% and Tmax1.However, the QL coated fabric shows higher Tmax2 and more left residue as compared to the corresponding P/A coated fabric, indicating the formation of more thermally stable char by the combination of PA-CNT with PHMGP/APP intumescent system.With increasing quadlayers coated on fabric, the burning time reduces gradually, and afterglow phenomenon disappears as well.Additionally, the coated fabric also leaves more unburned area and residual char with intact structure after combustion.Undeformed fibers are observed in 10 and 20 QL after burning, and numerous small bubbles appear on their residual fiber surfaces, indicating the formation of abundant expansion char during burning.It can also be seen that CNTs in the residue form a cross-linking network char on the fiber surface.This cross-linked network inhibits the inflation of bubbles, in favor of the formation of multicellular char.Thus, the enhanced flame retardant effect of this QL assembly coating is attributed to the formation of intumescent network structure during burning by introducing PA-CNT network into PHMGP/APP intumescent coating.Fourier transform infrared spectra and X-ray photoelectron spectroscopy of the residue char further reveal that the enhanced flame retardant effect on cotton is attributed to the powerful cooperative heat barrier action of intumescent flame retardant coating and CNT physical barrier layer, which is formed on the surface of fiber during burning.关键词：LBL self-assembly;Carbon nantube;Quadlayer;Flame retardant
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发布时间：2021-03-22 - 摘要：Fe3O4 magnetic nanoparticles coated by citric acid were synthesized via co-precipitation, and NH2-PEG-NH2-modified magnetic nanoparticles (PCMNPs) were thus prepared by carbodiimide chemistry to improve biological application of the nanoparticles. The surface morphology, chemical structures, crystal structures, thermostability and magnetic properties of the nanoparticles were characterized with scanning electron microscopy (SEM), Lorenz transmission electron microscopy (TEM), Malvern laser particle size analyzer, X-ray analysis (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Doxorubicin (DOX) was used as a model drug to study the PCMNPs drug loading and release behaviors, and DOX-loaded nanoparticles (PCMNPs-DOX) were then prepared, accordingly. The PEG modifier nanoparticles were roughly spherical with a relatively uniform size of about 15 nm. The size analysis showed that the as-synthesized magnetic nanoparticles were of statistical distribution with a maximal diameter of 33 nm. FTIR data and TG results all revealed that polymer PEG formed complexes on Fe3O4 surface. VSM result disclosed that no coercivity or remanence could be observed for samples, suggesting the superparamagnetic properties of the particles. The saturation magnetization (Ms) of the MNPs was about 68 A·m2/kg, which could be used for magnetic drug targeting delivery, hyperthermia treatment and magnetic resonance imaging. Consequently, the drug loading capacity in water was about 83%. The overall release efficiency was higher at a lower pH (5.0) than at physiological pH (7.4), which was important for the killing of relatively acidic tumor cells. Furthermore, the release of DOX from PCMNPs in both conditions showed that drug molecules released at a sustained pattern and complete release of drug was not attained. All the characterizations indicated that the PEG modifier nanoparticles showed superparamagnetic performance, high drug loading ability and sustained release behavior. Therefore, the as-synthesized magnetic nanoparticles could exhibit good drug loading and sustained-release effect, which provided a prospective method for cancer chemotherapy.关键词：Ferriferrous;Nanoparticles;Citric acid;PEG-diamine;Doxorubicin
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发布时间：2021-03-22 - 摘要：Hydrothermal treatment of polyamide 6 (PA6) fibers at 150℃ was studied.Different characterization and measurement were used to investigate the structural transformation and mechanical properties of PA6 fibers after hydrothermal treatment, which included two dimensional wide angle X-ray diffraction (2D-WAXD), two dimensional small angle X-ray scattering (2D-SAXS), differential scanning calorimeter (DSC), field emission scanning electron microscope (FE-SEM) and single fiber strength test.Under hydrothermal condition, the movement of the molecular chains was enhanced due to permeability of water molecules, which led to structure changes in PA6 fibers.After hydrothermal treatment, the crystal structure of the fibers transformed from γ into α phase, crystallinity degree increased from 25.2% to 45.9%, crystalline perfection was improved and crystallite size became bigger.Hence, the melting peak temperature of the fibers increased from 220.6℃ to 227.7℃ and the melting enthalpy also increased.In addition, the molecule chains in the amorphous region began to crystallize and grew along the radial direction of the fiber to form a crystal lamellae structure during hydrothermal treatment.At 150℃, ellipsoidal micro-pores formed in the fiber, which could be monitored by 2D-SAXS test.The hydrothermal treatment also caused changes of the fiber surface morphology.After the hydrothermal treatment, the smooth surface of the original fiber became rougher and a large number of macro-pores were formed on the surface.However, the micro-and macro-pores in fibers almost did not affect the melting temperature of the fibers.The crystal lamellae in fibers showed very weak orientation, but tensile could promote the lamellae orientation.When tensile strain increased from 0 to 50.7%, the average long period of lamellae increased from 10.6 nm to 14.8 nm.The hydrothermal treatment induced the reduction of amorphous region in the fibers and the formation of micro-and macro-pores, which resulted in the lower breaking strength and elongation of PA6 fibers.关键词：Polyamide 6;Hydrothermal treatment;Crystal structure;Thermal property;Mechanical property
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发布时间：2021-03-22 - 摘要：Diffusion and polymerization behaviour of styrene (St) in commercially-available high density polyethylene (HDPE) pellets were studied and HDPE/PS nanoblend pellets were synthesized.Both the diffusion and polymerization steps were carried out in water medium.At 70-90℃, diffusion behaviour of St towards HDPE pellets showed features of Fickian Diffusion.The saturation values of diffused St were different at different diffusion temperatures, and higher diffusion temperature meant higher saturation value, higher diffusion rate and shorter time to reach the saturation value.The amount of the initiator BPO was important in view of PS content in the pellets.With 0.5 wt%-1 wt% BPO, PS content was 11 wt% when diffusion and polymerization were carried out at 90℃, while the PS content increased to about 16 wt% when excess amount of BPO (5 wt%) was used.The diametrical distribution of PS was investigated by Micro Fourier Transform Infrared Spectroscopy, showing that PS appeared throughout the HDPE pellets.PS distributions along the diameters of the pellets showed similar "M" shape curves for HDPE/PS pellets synthesized with different amounts of BPO.The peaks of the curves appeared at 200 μm area to the surface and were related to crystalline structure of HDPE pellets.The phase morphology of PS in the blend pellets were characterized by field emission scanning electron microscopy.Typical sea-island morphology was revealed with an average particle size of less than 100 nm.The HDPE/PS blend pellets were melt-processed into cylindrical bars.PS phases in the extrusion bars of the blend pellets synthesized with 0.5 wt% BPO showed Ci Rice morphology, reflecting that PS particles were aggregating instead of coalescing during processing, and particle sizes were from tens of nm to 200 nm.The disperse PS phase and HDPE matrix had good interaction and the HDPE/PS bars did not break with elongation of 600% and showed higher tensile stress than pure HDPE bars, which meant that 0.5 wt% BPO was fairly good condition for preparing HDPE/PS nanoblends or other modified HDPE materials.关键词：Nanoblends;Diffusion;Phase morphology;High density polyethylene;Polystyrene
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发布时间：2021-03-22 - 摘要：Positively charged crosslinked polystyrene (PS) nanoparticles were first synthesized by emulsion polymerization using CTAB as emulsifier, and crosslinked PS nanoparticles/reduced graphene oxide hybrids (PS@rGO) were fabricated by electrostatic self-assembly, accompanied with in situ reduction.The obtained PS@rGO hybrids were incorporated into SBR matrix to fabricate SBR/PS@rGO composites.The structure and morphology of the composites were investigated.The results showed that GO was efficiently reduced by in situ reduction, and the obtained reduced graphene oxide (rGO) exhibited strong π-π interactions with PS nanoparticles.PS particles with their size of 60~70 nm were uniformly adsorbed onto the surface of rGO sheets, which effectively prevented rGO sheets from re-stack and aggregation.Then vulcanization performance tests further indicated that the inclusion of PS@rGO hybrids not only shortened the curing time (Tc90) by accelerating the vulcanization rate (CRI), but also improved the total crosslinking density of the composites.When 30 phr PS@rGO were introduced into SBR, the CRI was enhanced by 67.07%.And as expected, the morphology and performance analysis, and Mooney-Rivlin equation further demonstrated that PS@rGO hybrids were preferably dispersed in the matrix because of the synergistic effect resulted from PS and rGO, forming a 3D hybrid filler network in the rubber matrix.Also, it was reasonably concluded that the PS served as bridges connecting SBR matrix and rGO, resulting in strong interfacial interactions between PS@rGO and the rubber matrix.Thus, the improved filler dispersion and enhanced interfacial interactions greatly improved the mechanical performance and abrasion resistance of the SBR composites.For example, SBR/PS@rGO composites with a lower density exhibited higher mechanical performance and abrasion resistance in comparison with the SiO2 filled composites.These enhanced performances significantly conduce to reducing energy consumption under the dynamic condition, which further makes SBR/PS@rGO composites very promising in the application of rubber products, such as tire, etc.关键词：Crosslinked polystyrene nanoparticles;Graphene oxide;Electrostatic self-assembly;PS@rGO;SBR
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发布时间：2021-03-22 - 摘要：Polyvinyl formal (PVF) and polyvinyl butyral (PVB) as polymer frameworks are used to prepare quasi-solid-state electrolytes loaded with I2 and LiI, which are further applied in dye-sensitized solar cells (DSCs) to improve the stability of DSCs.FTIR spectra, thermodynamic and electrochemical methods are used to characterize the functional group of the polymers and the conductivity of the quasi-solid-state electrolytes.These results show that the oxygen atoms of C=O and O-C-O in the polymers (PVF and PVB) can interact with Li+ of LiI by coordination effect, promoting the ionization of LiI and facilitating the charge transport.Through the comparison between PVF and PVB, it can be also found that the propyl side chain of PVB has positive influence on the thermodynamic and electrochemical performance, where the DSCs with PVB exhibit better photovoltaic performance.By optimizing the composition of electrolytes, the ionic conductivity of PVF and PVB-based quasi-solid-state electrolytes can reach the maximum ionic conductivity of 2.5 mS·cm-1(PVF) and 4.2 mS·cm-1 (PVB), with the concentration of LiI at 0.7 mol·L-1.Under this condition, the diffusion-limiting current density of PVF and PVB-based quasi-solid-state electrolytes can achieve 10.05 mA·cm-2(triiodide ionic diffusion constant=1.84×10-6 cm2·s-1) and 17.89 mA·cm-2 (triiodide ionic diffusion constant=3.23×10-6 cm2·s-1), respectively.Impedance plots of the quasi-solid-state DSCs reflect that the PVB-based DSCs have a higher charge-transport resistance (Rct=118.9 Ω) than that of PVF-based DSCs (Rct=49.57 Ω) and effectively suppress the dark reaction due to the steric hindrance of the propyl side chain.Eventually, the dye-sensitized solar cells based on these two electrolytes attain satisfactory energy conversion efficiency of 4.18% (PVF) and 6.06% (PVB) and excellent long-term stability, which renders only a tiny decline of the efficiency of DSCs and maintain the efficiency of DSCs at above 90% of the original values.关键词：Polyvinyl formal;Polyvinyl butyral;Electrolyte;Conductivity;Dye-sensitized solar cell *
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发布时间：2021-03-22 - 摘要：High cis polybutadienes (cis-PB) with different molecular weights, molecular weight distributions (MWDs) and microstructures have been prepared via coordination polymerization of butadiene with rare earth catalyst system.The commercial cis-PB products (A9712, C9520 and C9634) were also selected for comparison.Isothermal crystallization kinetics and crystal morphology of cis-PB samples were investigated at various temperatures ranging from -18℃ to -27℃ by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) equipped with in situ heating and cooling device, respectively.The Avrami exponent (n) for various cis-PB samples was determined to be in the range of 2.0~3.0, which indicated that the isothermal crystallization of all the cis-PB samples proceeded via three-dimensional spherulite growth.The spherulites with different sizes and shapes could be observed for the cis-PB samples with different molecular weights, MWDs and cis-1, 4 contents.The size of spherulites increased with increasing cis-1, 4 contents of cis-PB samples under the same crystallization conditions.The half-crystallization time (t1/2) decreased and the crystallization rate increased with an increase in cis-1, 4 content of cis-PB samples by keeping the other conditions almost the same when the cis-1, 4 content of cis-PB samples was lower than 98.4%.However, the crystallization rate decreased with further increasing the cis-1, 4 content of cis-PB samples from 98.4% to around 99.0%.The crystallization could be greatly accelerated with simultaneous increases in molecular weight and cis-1, 4 content of cis-PB samples by keeping the polydispersity almost the same.The crystallization could also be accelerated with narrowing molecular weight distribution of cis-PB samples by keeping the molecular weight and cis-1, 4 content almost the same for the cis-PB samples.It was found that the degree of undercooling (ΔT), a driving force for crystallization, increased with increasing the cis-1, 4 content of cis-PB samples.The crystallization activation energy (ΔE) was determined to be in the range of -115~-140 kJ/mol.The negative values suggest that the crystallization could be accelerated with decreasing temperature.The ΔE values decreased from -115 kJ/mol to -130 kJ/mol with increasing the cis-1, 4 content of cis-PB samples from 95.2% to 98.2%, indicating that the crystallization rate could be increased more greatly with decreasing temperature for the cis-PB samples with higher cis-1, 4 contents when cis-1, 4 contents were lower than 98.2%.Moreover, the ΔE values kept at around -137 kJ/mol when the cis-1, 4 content of cis-PB samples was further increased from 98.2% to 99.0%, indicating that the dependence of crystallization rate on temperature was similar for the cis-PB samples with more than 98.2% of cis-1, 4 contents.关键词：High cis polybutadiene;Cis-1, 4 content;Isothermal crystallization kinetics;Crystallization activation energy;Equilibrium melting point *
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发布时间：2021-03-22 - 摘要：Structure-property and structure-function relationships for macromolecular thin films have attracted intensive research efforts.When tailored film thickness and the size of enwrapped macromolecules fall in the same order, nano-scale structural features are more prominent, which leads to significant change in macro-scale thermodynamical properties.The conformational distortions of macromolecules resulted from these nano-scale structural confinements, and the factor of chain entanglements within the polymer films are found in close causation with the dynamics of chains.The nature of macromolecule polydispersity has significantly complicated the situation.Nevertheless, there is few reported academic studies on corresponding mechanisms in the literature.In this paper, by virtue of Monte Carlo simulation jointed with primitive path analysis, we investigated the effect of polydispersity on the entanglement and dynamics of chains in thin macromolecular films.Specifically, a coarse-grained model of a bidispersed polymer melt under confined conditions was considered, and the focus was on the influence of weight fraction of relatively short chains on the entanglement and dynamics of long chains in polymer films.Our simulation indicated that, for higher weight fraction of short chain, the chain entanglements with low correlations could be easily released; and thus the confinement of neighboring particles dominated long-chain dynamics and caused it to decrease with decreased film thickness.In contrast, for lower weight fraction of short chains, the entanglement with high correlations was relatively hard to be released, the number and correlations of entanglements led to a nonmonotonic variation in long-chain dynamics with the film thickness.The usage of Monte Carlo simulation enables topological ergodicity, which leads to an efficient capture of macromolecular conformation.With the primitive path analysis of polymers under energy optimization, a physical picture demonstrating the relationship between polydispersity and chain entanglements/dynamics could be expected.关键词：Polymerthin film;Bidispersity;Chain entanglement;Dynamics;Monte Carlo simulation
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发布时间：2021-03-22
Research Article
- 摘要：A main chain thermotropic liquid crystalline polyester named poly (4, 4'-bis (6-hydroxyhexyloxy) binphenyl phenylsuccinate (PBDPS) reinforced by the combination of carbon nanotube (CNT, 1-dimensional carbon nanofiller) and graphene (G, 2-dimensional carbon nanofiller) was prepared in solution.Transmission electron microscopy was used to study the dispersion of the carbon nanofillers and morphology of the resulting nanocomposites.Interaction between two carbon nanofillers was observed, particularly for the nanocomposite with 2 wt% of CNT and G (PCNT1G1 (2%)).Raman and fluorescence spectrometry were used to investigate the π-π interaction between the carbon nanofillers and PBDPS chains.The phenomenon of fluorescence quenching and the dramatically decreased intensity of Raman absorption peaks confirmed the formation of π-π interaction between the nanofillers and PBDPS.Electronic universal testing machine was utilized to evaluate the tensile strength of the materials.The results suggested that due to the interaction between CNT and G, the mechanical properties of all composites were reinforced considerably.The addition of only 0.5 wt% CNT and G enhanced the tensile strength of the composites by 27.6% compared to pure PBDPS.With increasing the content of the carbon nanofillers, the tensile strength of the composites decreased gradually.Shape memory behavior and recovery stress were recorded by dynamic mechanical analysis, and it was found that the addition of CNT and G together considerably enhanced the shape recovery stress and maintained the shape fixing ratio effectively.The recovery stress of the composites was improved by 150% compared to pure PBDPS at the addition of 2 wt% of the nanofillers.On the other hand, both CNT and G exhibited negative effect on the chain mobility of PBDPS, especially with high content of the carbon nanofillers, thus decreasing the shape recovery ratios.关键词：Liquid crystalline polymer;Shape memory behavior;π-π Interaction;Carbon nanocomposite
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发布时间：2021-03-22
Research Bulletin
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