最新刊期
卷 ， 期 8 ， 2016
- 摘要：Due to the asymmetry of surface properties and shape features, Janus particles exhibit unique mechanical, optical, electrical, magnetic and amphiphilic properties, thereby demonstrating broad prospects for applications with respect to the construction of complex-assembled structures and the design of novel functional materials.In this review, recent progress on the rational design, tailored superstructures, and functionalities of self-assembling systems with Janus particles is systematically summarized, focusing on the perspective of simulation and theoretical analyses.From the aspects of the precise construction of the assembled structures and corresponding dynamic responses, entropy-driven regulation of the interfacial structures, nonequilibrium assembling dynamics, and the simulation and prediction of functionalities of the building blocks of Janus particles, the thermodynamic and kinetic mechanisms of the hierarchical assembled structures of Janus particles are elucidated, and the functionalities and potential applications of the polymer-matrix composites are introduced.Further, it is pointed out that the rational design of the asymmetric properties and the delicate control of the thermodynamic equllibrium of composites of Janus particles are the key to developing correspondingly novel functional materials.The future development and challenges of Janus particles are described finally.关键词：Janus particles;Hierarchical self-assembly;Entropy-driven regulation;Functional composites;Theory and simulation
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发布时间：2021-03-19 - 摘要：The physical and chemical properties of the hyperbranched polymers are similar to those of dendrimers, meanwhile, the hyperbranched polymers have some unique features, such as simple synthesis, broad molecular weight distribution, and the formation of their structures depends on the polymerization progress.The latest progress of simulation studies on kinetics of hyperbranched polymerization was reported in this paper.The dimensional bond fluctuation coarse-grained reactive lattice model was firstly developed to study the general rules of hyperbranched polymerization with the consideration of steric factors, intramolecular rings and the influence of the substituent effect.Furthermore, in order to quantitatively describe the structural information of monomer and polymer, a combined multiscale simulation method has been developed, and the coarse-grained force field is extracted with the method of iterative Boltzmann inversion.Then the coarse-grained reactive model combining the molecular dynamics and reactive Monte Carlo can be used to simulate the hyperbranched polymerization quantitatively.The multiscale model can be used not only for the accurate estimation of the general properties of hyperbranched polymers like degree of polymerization, polydispersity index and degree of branching, but also for achieving the important information of molecular structures, such as the intramolecular ring probability and the conformation of the hyperbranched polymer, and it is valuable in the fundamental research of hyperbranched polymerization.关键词：Hyperbranched polymerization;Coarse-grained force field;Monte Carlo;Multiscale simulation
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发布时间：2021-03-19 - 摘要：Wormlike chain model is one of so far the best theoretical models for the semiflexible biological polymer, liquid crystal polymer and conjugate polymer.The chain length is in the same length scale with the persistent length of semiflexible chains.In this condition, the orientation of bonds becomes important for the conformational statics and the in-extendable constraint decrease number of possible conformation of the chain.Structure factor characterizes the density correlation in different length scales, which can be obtained by both scattering experiment and theoretical computation.Generally, it is hard to compute the structure factor of wormlike chain model exactly, because it has the degrees of freedom in both positional and orientational space.This strangles the development of theory based on wormlike chain model, especially, applying Gaussian fluctuation theory on the stability analysis of ordered systems.In this review, the commonly used approximated formulations of structure factor of wormlike chain model are introduced and the development on predicting the structure factor exactly.Through analyzing the scaling relation in different wavenumber regions, the multi scale properties of wormlike chain model are well demonstrated.关键词：Semiflexible chain model;Wormlike chain model;Structure factor
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发布时间：2021-03-19 - 摘要：The formation of novel ordered morphological structures from a microphase separation process enables diverse and expanding applications of block copolymers in areas such as nanolithography, drug delivery, and solar cells.How to manipulate the formation and stability of these structures is a key facter for application in the field of block copolymers.Recent reports from both experiments and theoretical works predicted that the polydispersity in block length distribution has a pronounced effect on many aspects in the phase behavior of block copolymers.Based on the introduction of developments in the experimental and theoretical works, this article gives a mini review especially on the recent developments in simulation works for polydisperse AB diblock and ABA triblock copolymers via the dissipative particle dynamics simulation techniques.An outlook of possible future researches on the issue of the polydispersity effects on more complex block copolymer systems is also given.关键词：Block copolymer;Microphase separation;Polydispersity;Dissipative particle dynamics simulation
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发布时间：2021-03-19 - 摘要：Dissipative particle dynamics (DPD) is an established method for mesoscale coarse-graining fluid simulations, and has a broad range of applications in studies of micro-and nanofluidics.The method is fully off-lattice and particle based and naturally includes thermal fluctuations.Due to the importance of surface interaction, the choice of boundary condition is essential to micro-and nanofluidic researches.No-slip boundary condition, where the fluid velocity vanishes at a fluid/solid interface, is widely accepted for macroscopic fluids.A more general boundary condition is the Navier boundary condition, which allows fluid to slip.Here we briefly reviewed the DPD method and the tunable-slip method that implements the Navier boundary condition.The applicability and reliability of the simulation methods are demonstrated using two examples:one is the study of flow over a superhydrophobic surface with striped pattern.The simulation results show good agreement with the theoretic and numerical predictions.The second example is the polymer dynamics in a microfluidic device.The modification of the boundary condition can induce different polymer dynamics under confinement.Both examples demonstrate that DPD simulations can provide guidance in the design of better and efficient micro-and nanofluidic devices.关键词：Dissipative particle dynamics;Tunable-slip boundary condition;Micro-and nanofluidics;Computer simulation
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发布时间：2021-03-19 - 摘要：Block copolymer-nanoparticle composite nanomaterials provide exciting opportunities as they may display distinctive properties from constituents that are desired in applications including biomedicine, photoelectric materials, and catalytic materials, etc. Block copolymers can self-assemble to various nanoscale structures.The successful distribution of nanoparticles in a particular location of the block copolymer matrix can improve the functional properties of nanoparticles.In this review, the methods for fabricating block copolymer-nonaparticle composite nanomaterials are introduced.Experimental and theoretical progress in the description of these nanostructured block copolymer based hybrid materials is represented.Furthermore, precise assembly and localization of nanoparticle in block copolymer assemblies are of great importance in realizing the formation of nano-hybrids with high performance.The properties and applications of the nanocomposites depend not only on those of individual building blocks but also on their spatial distribution within different morphological aggregates at different length scales.This review also discussed the effect of nanoparticle size, shape and surface chemistry on the selective localization of nanoparticle within block copolymer aggregates.Those factors manipulate the balance between enthalpic and entropic contributions, which provides an opportunity to precisely control the spatial distribution of nanoparticles in block copolymer aggregates.In the end, the self-assembly of block copolymer-nanoparticles in theoretical simulation is introduced.Theoretical and computational simulations offer a unique approach not only to study the evolution and formation of nanostructures, but also to investigate structure-property relationship of hybrid nanocomposites.关键词：Block copolymer;Self-assembly;Nanoparticle
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发布时间：2021-03-19 - 摘要：Complex Langevin (CL) theory of polymer is beyond mean-field simulation, which enables to obtain ensemble averages of physical quantities of polymer systems including fluctuation and correlation effects.As the Hamiltonian of polymer field theory is usually complex, the corresponding Boltzmann factor is non-positive defined.Therefore, instead of the regularly important sampling method, like Monte Carlo, we use the complex Langevin equation to make sampling in the whole complex plane, where a positively defined Boltzmann factor is assumed to be existed.It is shown in this review that complex Langevin simulation is much more efficient than regular sampling methods for studying of polymer systems.Such a method beyond mean-field simulation is very important to study dilute polymer solution, polyelectrolytes systems, in particular, to predict new phases of block copolymer systems, of which mean-field simulations, like self-consistent field theory (SCFT), have been demonstrated to be not enough in studying these problems.In this review, we give a brief introduction of the complex Langevin simulations.We focus on its theoretical background and the numerical way of how to conduct CL simulations.We show two examples to indicate the advantages of the method beyond mean-field simulation, where fluctuation and correlation effects have been clearly obtained by the CL simulations but missing in SCFT calculations.Complex Langevin simulation has advantages not only in polymer systems but also in ionic systems especially for multi-valence ionic systems.Moreover, developing a method beyond mean-field simulation is also important for biological systems, like understanding the DNA condensation phenomena, the charge inversion inside the virus, and so on.关键词：Polymer field theory;Complex Langevin simulation;Beyond mean-field simulation
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发布时间：2021-03-19 - 摘要：With regard to polymer nanocomposites (PNCs), here we systematically review the achievement and progress of dispersion of nanoparticles (NPs) and the interfacial interaction between polymer-NPs through computational simulation technique, including the dispersion mechanism (four categories:depletion attraction leading to contact aggregation; segment level tight particle bridging; steric stabilization due to thermodynamically stable "adsorbed bound polymer layers"; "tele-bridging" where distinct adsorbed layers coexist with longer range bridging effect), phase behavior and the micro-structure of various shapes of NPs in the polymer matrices, the effect of the NPs on the chain conformation (the change of the mean squared radius of gyration of polymer chains), the chain structure on the surface of the NPs (orientation and alignment), the interfacial interaction between polymer chains and NPs, and the chain translational and rotational dynamics in the interfacial regions between polymer and NPs, and the network structure formed via NPs.These simulated results serve a basis for further designing and fabricating PNCs with excellent properties.To comprehensively construct the relation between the component, structure and property of PNCs, we put forward three simulation challenges, including developing the simulation technique at long time and large length scales, establishing the accurate approaches to simulate the mechanical properties and functional properties such as thermal and electrical conductivities.关键词：Polymer;Nanoparticles;Interface;Dispersion;Reinforcement;Simulation
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发布时间：2021-03-19
Feature Articles
- 摘要：Polyurethane acrylate(PUA) based on polyether-ester have potential applications in tissue engineering, artificial scaffold, and other medical devices.Polyether ester diol triblock copolymers (PLLA-PEG-PLLA, PLEL) were synthesized by ring opening polymerization of L-lactide(L-LA) with the presence of polyethylene glycol (PEG).It is also used as soft segments for the preparation of polyurethane acrylate (PUA) oligomers containing PLEL-diol, diisocyanate (isophorone diisocyanate IPDI and hexamethylene diisocyanate HDI) and hydroxyethyl methacrylate (HEMA).PLEL-diols and PUA oligomers were characterized by 1H-NMR and GPC.The PUAs were fabricated under UV light, followed with structure and morphology analysis (DSC and DMA) and hydrophilic property characterization (contact angle and swelling).The results showed that increasing length of hydrophobic PLLA in PLEL-diols reduced PUA hydrophilicity, crosslink density and biodegradation rate.With the same soft segment, PUA made from hard segment of HDI-HEMA showed higher hydrophilicity and biodegradation rate than PUA based on IPDI-HEMA, because of a cyclic structure of IPDI reducing the interaction with water.The degradation experiment indicates that the PUA membranes degraded most rapidly in PBS/H2O2/CoCl2 solution, then slower in lipase solution, and lowest in pure PBS solution.The oxidative degradation rate of PUA materials depended on the content of PEG in the soft segment.The highest weight loss of 82.62% was recorded from the PLEL1000-HDI (the highest PED content in the PUA) degradation experiment in 13 weeks.关键词：Polyether ester;Polyurethane acrylate;UV-curing;Oxidative degradation;Enzymatic degradation
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发布时间：2021-03-19 - 摘要：A novel method for the "green" synthesis of PMAA nano-hydrogels in water was developed.In the method, small poly(methyl methacrylate) (PMMA) nanolatex particles formed "in situ" were used as the seeds.Meanwhile, the hydrogen bonding interactions between the surfactant tween 20 on the surfaces of the seeds and MAA monomers were utilized to realize the selective polymerization of MAA on the surfaces of the PMMA seeds, thus resulting in the formation of PMAA nano-hydrogels with PMMA cores and cross-linked PMAA shells.Magnetic PMAA nanoparticles were further fabricated by an "in situ" oxidization precipitation method.The size and size distribution, composition, morphology, structure, pH-response behavior and magnetic property of the resulting PMAA nano-hydrogels and magnetic PMAA nanoparticles were characterized.The hydrogen bonding interactions between tween 20 and MAA (PMAA) prompt the selective growth of a crosslinked PMAA layer on the surfaces of PMMA seed latex, resulting in the formation of PMAA nano-hydrogels with PMMA cores and cross-linked PMAA shells.The core-shell structure of the PMAA nano-hydrogels was disclosed by TEM observations.The PMAA nano-hydrogels display excellent pH-responses:as the pH value increases from 1 to 6, the expansion of their hydrodynamic volumes approaches 50 times.The magnetic PMAA nanoparticles were superparamagnetic and with a saturation magnetization as high as 50 A ·m2/kg.关键词：Poly (methacrylic acid);Nano-hydrogels;pH-response;Magnetic response;Synthesis
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发布时间：2021-03-19 - 摘要：Recently site-specific and stoichiometric modification of proteins with synthetic polymers has attracted a great deal of attentions in numerous fields, such as material science, nanotechnology, biomedicine, diagnostics, and so on.In this work we describe the growth of a brush-like polymer from the N-terminus of proteins via the atom transfer radical polymerization (ATRP) of oligo(ethylene glycol) methacrylate (OEGMA) under mild conditions.Bovine serum albumin (BSA) was used as model protein.The N-terminus of BSA was firstly modified with pyridoxal-5-phosphate (PLP).Then reacted with a hydroxylamine-functionalized ATRP initiator (i.e., (2-(aminooxy)ethyl) 2-bromo-2-methylpropanoate, ABM), formed the so called macroinitiator (i.e., BSA-Br).After that, ATRP was successfully carried out on the BSA-Br macroinitiator using OEGMA as monomers, giving rise to a BSA-POEGMA conjugate.The resulting compounds were characterized using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), ultraviolet-visible spectroscopy (UV-Vis) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS).The FTIR and 1HNMR results clearly indicated the successful synthesis of ABM.The UV-Vis spectrum of BSA-Br showed a new absorption peak at λ=328 nm compared to that of pure BSA, which suggested the coupling between BSA and ABM.MALDI-TOF-MS data showed that two ABM molecules were coupled with BSA.The synthesis of the stoichiometric (1:2) BSA-POEGMA conjugate was also confirmed by means of FTIR, UV-Vis and MALDI-TOF-MS measurements.The degree of polymerization (DP) for POEGMA segment was calculated to be 105, which was close to theoretical value (i.e., DP=100).关键词：Protein-polymer conjugate;Bovine serum albumin;Poly (oligo(ethylene glycol) methacrylate);Atom transfer radical polymerization
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发布时间：2021-03-19 - 摘要：Effects of carbon black(CB) particle distribution, feeding sequence and blending time on the electrical conductivity of high density polyethylene(HDPE)/ethylene-vinyl acrylate copolymer(EVA) blends filled with CB were investigated by using scanning electron microscope(SEM) and transmission electron microscope(TEM).The results reveal that CB particles distribute selectively in HDPE phase due to better flexibility of HDPE chains than that of EVA.Feeding order significantly influences the electrical conductivity of the composites by affecting the distributed status of CB particles in the two immiscible phases, i.e.HDPE phase and EVA phase.In order to gain high electrical conductivity, CB should be firstly added into EVA and then HDPE is added, or EVA and HDPE are initially blended uniformly and then CB particles are added.Blending time also has remarkable effect on the electrical conductivity of the composites.With the increase of blending time, the electrical resistivity of all the polymer composites with different feeding sequences decreases firstly and then increases.In later stage of blending, the electrical resistivity of HDPE/EVA-CB changes slightly with blending time compared with the other two blend systems.The phase morphology evolution dominates the conductivity of HDPE/CB-EVA during blending, however, distribution of CB particles dominates the conductivity of HDPE/EVA-CB.To achieve better electrical conductivity, appropriate feeding sequence and blending time should be adopted.关键词：Carbon black;High density polyethylene;Ethylene-vinyl acrylate copolymer;Conductive polymer composite;Processing technology
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发布时间：2021-03-19 - 摘要：By using the periodically sampling approach and UV spectrophotometry the conversion of acrylamide and the content of the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyeth-oxy)phenyl]-1-acetone in the polymerization process were measured.There are three stages in the photo-polymerization process of acrylanide, according to the acrylamide conversion rate and the corresponding initiator content.A three-stage model of polymerization process was established by the photoinitiator consumption, and the polymerization process was divided into the initial period of polymerization, the polymerization period and the later period of polymerization.The decomposition kinetics of photoinitiator was investigated with a homemade photopolymerization instrument.The initiator decomposition rate constant (kd) was calculated under different conditions.The results show that, photoinitiator decomposition rate constants kd within 4.00×10-4 s-1 can be regulated under the experimental conditions, and there is a best kd combination in the three-stage model, that is, the kd of a first stage was 4.00×10-4 s-1, the kd of the second stage was 1.90×10-4 s-1, the kd of the third stage was 1.90×10-4 s-1.The optimal free radicals concentration of synthesis of polyacrylamide (PAM) is 10.82×10-8~12.56×10-8 mol ·L-1s-1.Photoinitiator initial concentration[I]0 should be controlled at 100~110 mg/L.关键词：Photoinitiator;Dynamics;Polymerization process;Polyacrylamide
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发布时间：2021-03-19 - 摘要：The ceramic (Zr/Ti)B2 particles with high thermal conductivity were introduced into epoxy matrix for the preparation of epoxy composites by in situ polymerization method.The laser flash method was taken to investigate the thermal conductivity of the epoxy composites, and a numerical analysis was applied to build up an ideal model for further discussion as well.The experimental results demonstrate that the introduction of TiB2 and ZrB2particles can improve the thermal conductivity of the epoxy composites effectively.And within a certain range, the thermal conductivity of the epoxy composites was improved with the increasing content of the diboride ceramic fillers.The improvements of thermal conductivity of the epoxy composites filled with TiB2 and ZrB2fillers were up to 100.7% and 126.8%, respectively, compared to the neat epoxy resin.Besides, the epoxy composites filled with ZrB2fillers show higher values of thermal conductivity than the TiB2-filled ones, which is attributed to the lower interface resistance in the ZrB2-epoxy system.The results of the numerical analysis exhibit that the experimental values of thermal conductivity of the epoxy composites are similar to those calculated in ideal models, where the deviations between experimental and ideal values in ZrB2-filled epoxy composites are smaller than those in TiB2-filled epoxy composites at high fractionlevels of the fillers.关键词：Polymer matrix composites;TiB2/ZrB2;Thermal conductivity;Finite element analysis
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发布时间：2021-03-19 - 摘要：The electrospun polyacrylonitrile (PAN) nanofibers were chemically modified with amidoxime groups by reacting with hydroxylamine hydrochloride into amidoxime-modified PAN (AOPAN).SEM, FTIR and water contact angle test were used to characterize its physicochemical properties, and then AOPAN was applied for Cr(VI) ions adsorption.The results show that AOPAN nanofibers swelled and bended to a certain degree after hydro-thermal treatment at 60℃for 3.5 h.In the FTIR spectra, the double peaks at 3500-3300 cm-1are ascribed to the typical-NH2 absorption peak.And the water contact angle decreased from 114.5° to 29.8°.It suggests that the AOPAN nanofibers were obtained through this method.The Cr(VI) adsorption test shows that the adsorption capacity of AOPAN nanofibers is as high as 102.5 mg/g at pH=2 and the adsorption equilibrium can be quickly reached within 5 h.This is mainly due to the protonation of-NH2 groups under the acid condition, which is benefit for adsorbing HCrO4-.Moreover the AOPAN nanofibers maintained over 50% removal rate after rinsing with dilute NaOH solution by four cycles.Thus, these AOPAN nanofibers have a high recyclable ability and are promising in heavy metal ions adsorption.关键词：Electrospinning;PAN;Dichromate;Surface modification
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发布时间：2021-03-19 - 摘要：Acrylic polyols with polyethylene glycol (PEG) side chains (BOH) were synthesized with allyl polyethylene glycol (APEG), methyl methacrylate (MMA) and butyl acrylate (BA).The α, ω-triethoxysilane terminated PDMS oligomer (TSU), and α, ω-triethoxysilane terminated PFPE oligomer (PFU) were synthesized, respectively.Then the oligomers were mixed together to prepare the crosslinked-network coatings by condensation reaction.The chemical composition of the as-prepared copolymer was characterized by 1H-NMR and FTIR.Surface energy, elastic modulus and the biological fouling properties of the coatings were measured by the X-ray photoelectron spectroscopy, contact angle (water and diiodomethane), nano mechanical test instruments and biofouling assays.The effects of the surface energy, elastic modulus and biological fouling properties of the copolymer were investigated.The results showed that the crosslinked network coatings had both lower surface energy attributed to fluorine and silicone elements, and better antifouling properties thanks to PEG side chains.Thus their antifouling properties were better when comparing with hydrophilic BOH and the commercial sample DC 3140.关键词：Addition polymerization;Anti-fouling;Cross-linked network coatings;Amphiphilic polymer
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发布时间：2021-03-19 - 摘要：Ethynyl phenyl azo novolac foam (EPANF) was prepared by high temperature foaming.Structure of ethynyl phenyl azo novolac resin (EPAN) was characterized by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC).Optical microscopy, scanning electron microscopy (SEM), thermal conductivity analyzer, critical oxygen index analyzer and thermal analysis (TG) were used to examine the morphology, compression strength, thermal insulation, flame retardant and thermal properties, respectively.With 18% of blowing agent and apparent density of 0.179 g/cm3, fine and uniform morphology was obtained for EPAN sample of average diameter around 350μm.Among those properties, compressive strength, coefficient of thermal conductivity and critical oxygen index (which is an indication of flame retardation) were proportional to apparent density of EPANF.As apparent density of 0.363 g/cm3, compression strength was up to 5.63 MPa.However, heat insulation performance was decreased slightly with the increase of apparent density.TG showed that there were two exothermal reactions with mass losses of 5% and 10% that occurred at 333 and 381℃, respectively.Char yields at 700 and 1000℃were measured to be 65.8% and 58.2%, respectively.There are significant improvements in both heat and ablation resistance compared with the use of ordinary novolac phenolic resin.As a potential thermal structure and ablative resistant material, EPANF was expected to find wide applications in aerospace and related fields.关键词：Ethynyl phenyl azo novolac resin;Foams;Structure;Property;Heat resistant property
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发布时间：2021-03-19 - 摘要：The water-soluble azo initiator, 2, 2'-azobis (2-methylpropiondodecylamidine) dihydrochloride (AIBL), with twelve alkyl carbon chain at the both ends, was prepared through Pinner reaction, using AIBN and n-Dodecylamine as main reactants.The structure and purity of AIBL were characterized by 1H-NMR, elemental analysis (EA) and HPLC.The thermal decomposition and thermal decomposition kinetics were studied with DSC, TGA and UV spectrophotometer.The surface activity was determined by surface tension-meter.These results show that the synthesized initiator AIBL has a desirable structure and a high purity.Its thermal decomposition belongs to the first order reaction with the activation energy of thermal decomposition is 134.80 kJ/mol, and the half-life period of it at 70℃in water is about 4 h.Its aqueous solution shows that the surficial activity with the CMC is 0.13 g/L and the corresponding surface tension is 33.57 mN/m.The hydrophobically end-capped aqueous polymers SPAM were prepared using acrylamide as monomer and AIBL as initiator agent.The conversion rate of AM was studied by using the bromide method.The association effect of SPAM was studied with Ubbelohde viscosity, zero shear viscosity and fluorescence probe.The results show that AIBL has favourable ability to initiate polymerization of acrylamide.SPAM, compared with PAM which was synthesized by Initiator without hydrophobically long chain, has obviously hydrophobically associative effect, which indicated that AIBL has successfully introduced the hydrophobically long chain into the polymer end, forming hydrophobically end-capped polymer.关键词：Initiator;Azobis(2-methylpropiondodecylamidine) dihydrochloride;Thermal decomposition;Water solubility;Hydrophobically end-capped polymer;Hydrophobic association
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发布时间：2021-03-19 - 摘要：The polylactic acid (PLA) grafted cellulose copolymer (OLA-g-C) was synthesized by melt copolycondensation of lactic acid with microcrystalline cellulose (MCC), then PLA/OLA-g-C blends and contrast samples PLA/MCC blends were prepared by solution mixing.The results of scanning electron microscopy (SEM) showed that the existence of PLA side chains improved the dispersion of cellulose in PLA matrix and inhibited the agglomeration.In non-isothermal crystallization process, OLA-g-C and MCC both promoted the crystallization ability of PLA, but the promotion effect of OLA-g-C was better than MCC due to the well dispersion of OLA-g-C in PLA matrix.In isothermal crystallization process, OLA-g-C can accelerate the crystallization rate and improve the crystallinity simultaneously, but had no influence on the growth geometry and nucleation type of the crystal of PLA.The results of polarized optical microscopy (POM) further proved that OLA-g-C as the nucleating agent, reduced crystallization time, and enhanced the crystallization ability of PLA.However, the elongational viscosity decreased with the addition of OLA-g-C, which related to the entanglement between OLA-g-C and PLA matrix.关键词：Cellulose;Polylactic acid;Crystallization;Elongational viscosity
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发布时间：2021-03-19
Research Article
- 摘要：Using acetone as a solvent, a dinitro compound 9, 9-bis(3-nitro-4-hydroxyphenyl) fluorene was synthesized by the nitration reaction of 9, 9-bis(4-hydroxyphenyl) fluorene (BHF) using concentrated nitric acid at room temperature.And then, 9, 9-bis(3-amino-4-hydroxyphenyl) fluorene (BAHF) was obtained via the catalytic reduction with hydrazine hydrate and Pd/C.The copoly(amic acid) containing phenolic hydroxyl was synthesized from the diamine BAHF, 9, 9-bis(4-aminophenyl) fluorene (BAF) and 4, 4'-hexafluoroisopropylidinedi(phtalic anhydride) (6FDA) via the low-temperature solution polycondensation reaction.The thermally induced rigid membrane materials of copolyimide (CPI) and poly(imide-benzoxazole) (PI-PBO) were prepared by the thermal imidization and thermally induced rearrangement reaction.The structure, thermal properties and gas separation performance of these membrane materials were characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), differential scanning calorimetry (DSC) and gas permeation performance testing means.The experimental results show that these thermally induced rigid membranes mainly exhibit amorphous structure, and the glass transition temperature (Tg) is about 340℃.It means that the CPI was a random copolymer.With the increase of thermal treatment temperature, the gas permeabilities of H2, O2, N2, CH4 and CO2 of thermally induced rigid membranes increased gradually.When the thermal treatment temperature reached 450℃, the gas permeabilities of O2, N2, H2, CH4 and CO2 of the thermally induced rigid membrane were 229.03 and 53.26, 1497.35, 33.52 and 818.76 Barrer separately.These thermally induced rigid membranes containing bulky fluorene and hexafluoroisopropyl groups could be expected to be used in the gas separation applications.关键词：Copolyimides;Thermally induced rigid membrane;Gas separation;Fluorene;Phenolic hydroxyl
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发布时间：2021-03-19
Research Bulletin
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