最新刊期
卷 ， 期 10 ， 2015
- 摘要：To make the nucleating agent and the strain-induced crystallization work synergistically,the effect of nucleating agent on the strain-induced crystallization of poly(lactic acid) (PLA) films is investigated.Amorphous film samples of pure PLA (T0) and PLA/TMC328 (specialized nucleating agent) blends with different contents of TMC328 (0.5 wt%,1 wt% denoted as T0.5,T1) are prepared and characterized by X-ray diffraction (XDR) and differential scanning calorimetry (DSC).Then they are drawn at temperatures of 80 and 90 ℃,about 24~34 K above Tg.And the crystallinity of drawn samples is measured by DSC and Fourier transform infrared spectroscopy (FTIR).Unexpected,at 80 and 90 ℃ the crystallinity of T0 is much higher than those of T0.5 and T1,even though the nucleating agent can improve the cold crystallization of PLA significantly at 90 ℃.Moreover,the strain-induced crystallization works better and more stably at Td of 80 ℃ than at Td of 90 ℃.Then a new crystallization mechanism can be presented,which is independent of nucleation density even nucleation,but dominated by the formation and retention of strain-induced regular conformation.And the strain-induced crystallization works better with lower Td,at which the intensity of the chain thermal motion is weaker and the formation of regular conformation can be easier.Therefore,during the process of strain-induced crystallization,the nucleating agent diffusing between the PLA chains plays a role of impurity which impedes the formation of regular conformation of PLA chains.So the synergy of improving crystallization cannot be achieved by the addition of nucleating agent.关键词：Train;Nucleating agent;Strain-induced crystallization;Arrangement of chains
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发布时间：2021-03-19 - 摘要：Biomimetic thiol terminated glycopolymers PGAMA-PCL-SH were effectively anchored on the surface of gold nanorods to prepare the biomimetic glycopolymers modified gold nanoparticles (Gly@Au NRs).UV-Vis,XPS,DLS and TGA were used to characterize Gly@Au NRs.NIR-induced heating of an aqueous suspension of Gly@Au NRs was performed.Then,curcumin (CUR) was loaded into Gly@Au NRs and the in vitro release of CUR was studied.We found that the NIR-laser irradiation can control the drug release effectively.Moreover,cell viability studies revealed that the cytotoxicity of the Gly@Au NRs complexes was remarkably improved as compared to that of the original Au NRs.Consequently,the Gly@Au NRs complexes can be used as biocompatible vehicles to realize the controlled drug release by remote NIR-laser irradiation.关键词：Glycopolymer;Gold nanorods;Controlled release
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发布时间：2021-03-19
Rapid Communications
- 摘要：Reactive force field (ReaxFF) molecular dynamics simulation was adopted to study the pyrolysis mechanism of polyurethane/vinyl ester resin (PU/VER) at an atomic level.The reaction systems,containing 1395 atoms,were simulated at various heating rates and temperatures,ranging from 100 K/ps to 500 K/ps and 2800 K to 4800 K respectively.The relevance between the simulation results and the experimental observations was also discussed.In the pyrolysis process,due to the initial dissociation of the PU-modified OO bonds,the branched chains including CN were separated from the main chains.Then the oxygen-bridge bonds in the main chains broke subsequently,which presented the primary cause of vinyl resin main-chain scission.Hence,the consecutive chain reaction would ultimately lead to the de-polymerization of the entire polymer structure.Because of intensive activity of the carbon-carbon double bonds,the vinyl (H2C=CH) at the end of PU/VER main chains was involved in the generation process of the final three dominant products,including hydrogen (H2),carbon dioxide (CO2) and acetylene (C2H2).Furthermore,the primary products and the corresponding generation paths of PU/VER pyrolysis extracted from the ReaxFF simulations coincided well with the experimental observations.The proposed research demonstrates that,the ReaxFF-based simulation methodology can provide deep insight into the chemical reaction mechanisms in polymer pyrolysis.关键词：Wind turbine blades;Polyurethane/Vinyl Ester Resin;High temperature pyrolysis;ReaxFF;Reactive molecular dynamics
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发布时间：2021-03-19 - 摘要：Two diamino silicon-containing compounds 3,3'-(1,3-dimethyl-1,3-divinyl-1,3-disiloxanediyl)bis(benzenamine) (S1) and 4,4'-(1,3-dimethyl-1,3-divinyl-1,3-disiloxanediyl)-bis(benzenamine) (S2) were synthesized and used as the novel curing agents of DGEBA epoxy resin with an epoxy value of 0.51 (E51). The curing kinetics were studied by non-isothermal differential scanning calorimetry (DSC) technology. Curing processes of the two systems were determined according to the change of characteristic temperature at different heating rates as 100 ℃/1h+160 ℃/2h+190 ℃/3h for E51/S1 and 110 ℃/1h+170 ℃/2h+190 ℃/3h for E51/S2. The curing parameters including activation energy E, Arrhenius frequency factor A and reaction order n were analyzed by Kissinger equation, Crane equation and Arrhenius equation. E is 50.65 kJ/mol, A is 1.83105, n is 0.87 for E51/S1; E is 51.39 kJ/mol, A is 1.44105, n is 0.87 for E51/S2. According to the value of E and A, the reaction activity between E51 and S2 is higher than that of E51 and S1, in other words, it is easier for ring open reaction when NH2 in the para position of benzene ring. The reaction orders of E-51/S1 and E-51/S2 are the same and both less than 1, implying that the curing reaction is complicated. And nth-order curing models of the curing systems were obtained based on the curing kinetics parameters.关键词：Diamino disiloxanes;Synthesis;Epoxy resin;Curing kinetics
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发布时间：2021-03-19 - 摘要：Novel pH-responsive cellulose papers have been prepared via grafting poly(2-(dimethylamino)ethyl methacrylate) (PEMAEMA) from the conventional filter papers by ARGET (activators regenerated by electron transfer) ATRP (atom transfer radical polymerization).The grafting polymerization was conducted in anisole and methanol respectively,and a relatively higher grafting efficiency was achieved in methanol.A sacrificial initiator was used when performing the reaction.The free polymer,formed from the sacrificial initiator in parallel to the grafting on the papers,was characterized by GPC,showing that the length of the polymer chains increased with increasing reaction time,and the molecular weight distribution index was between 1.4~1.6.The grafted filter papers were evaluated with FTIR,SEM and graft ratio,suggesting that ARGET ATRP provided a good control for the grafting of PDMAEMA,and the amount of polymer on the surfaces could be tailored by polymerization time.Water contact angle measurements implied that the papers presented obvious pH-responsive properties after the grafting.The wettability of the PDMAEMA-grafted papers varied with changes in pH,and the hydrophobic ability was enhanced when the pH was improved.关键词：Poly(2-(dimethylamino)ethyl methacrylate);ARGET ATRP;pH-Responsive;Cellulose papers
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发布时间：2021-03-19 - 摘要：A molecular dynamics simulation study was performed to analyze the interactions between epoxy resin monomers and carbon nanofiber (CNF) surface.The epoxy resin monomers included diglycidyl ether of bisphenol-A (DGEBA) and isophoronediamine (IPD).The results showed that an epoxy resin monomers interphase was formed on the CNF surface due to the adsorption between the CNF surface and epoxy resin monomers.The concentration of monomers in the interphase is higher than that in the bulk phase.And the concentration of IPD monomers in the interphase was much higher than that in the bulk phase,while the concentration of DGEBA monomers in the interphase was lower than that in the bulk phase.In the interphase,the molecular structure of DGEBA monomers was more extended than that in the bulk phase,while the structure of IPD monomers was unchanged compared with that in the bulk phase.The movements of DGEBA and IPD monomers in the interphase were inhibited by the CNF surface,and the inhibition in the direction perpendicular to CNF surface was the strongest.The density of binding energy showed that the bonding strength of IPD monomers with CNF surface was higher than that of DGEBA monomers,which was in good agreement with the previous results.关键词：Molecular dynamics simulation;Epoxy resin;Carbon nanofiber;Interphase;Interaction
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发布时间：2021-03-19 - 摘要：Three kinds of spirooxazine compounds (SP1~SP3) that have photochromic properties were designed and synthesized.They contain similar groups(CH2)n Br with different numbers of carbon.Compounds SP1~SP3-hPMMA were prepared by respectively reacting compounds SP1,SP2 and SP3,containing reactive CBr bond,with polymethyl methacrylate (PMMA) of different hydrolysis ratios.The structures of these target compounds were characterized by 1H-NMR and IR tests.The photochromic properties and factors that influence photochromic properties of the SP1~SP3 and SP1~SP3-PMMA were investigated.The influences of hydrochloric acid concentration and PMMA of different hydrolysis ratios on photochromic properties and thermal stability of target compounds were studied.The results show that compound SP3 with a longer carbon chain has better photochromic properties and thermal stability than compounds SP1 and SP3.Moreover,the fading rate of SP-hPMMA is obviously lower than that of SP.With the increase of hydrochloric acid amount,SP-5%hPMMA maximum absorption and fading time increase.HCl further enhances the thermal stability of SP-hPMMA.Especially,SP3~9%hPMMA has the best photochromic properties and thermal stability in comparision with the others.Properties of films of SP-PMMA were also studied.Above all,it is expected that SP-9%hPMMA will be applied in the field of polymer photochromic materials.关键词：Pirooxazine;Photochromical compound;Thermal stability;PMMA
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发布时间：2021-03-19 - 摘要：The temperature dependent stress-strain curves of Nylon 6 were obtained via tensile hot stage,and the in situ WAXS experiments were measured simultaneously.The results indicated that the temperature related yield stress,breaking strength and modulus of Nylon 6 can be described by the Arrhenius equation.During the process of stretching Nylon 6 experienced elastic deformation,yield,strain hardening and fracture.The yielding on Nylon 6 stress-strain curves was unobvious with the low draw rate,meanwhile,the yielding turned to more unobvious gradually at higher stretching temperatures.The stress-strain curves of Nylon 6 are similar to each other within the measured temperature range.Nevertheless,the yield strength and modulus decreased with the increasing of stretching temperature.By analyzing the WAXS profile,it was found that the -phase: -phase ratio of undeformed Nylon 6 samples decreased along with the temperature increased.Also,at high temperatures,the crystalline phase of Nylon 6 slipped and/or melted during tensile deformation more easily.In the meantime,the relationship between the stretching temperature and mechanical properties was obtained after fitting the temperature dependent results.It was found that the temperature related relationship obeys the Arrhenius equation.In addition,the viscosity dependence of yield stress was given in the paper.关键词：Nylon 6;Temperature related stress-strain curves;Structure transitions;in situ WAXS
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发布时间：2021-03-19 - 摘要：The lead p-aminobenzoic acetate (ABA(Pb)) was synthesized via ion exchange method,and then lead-ion-containing polyamide acid (PAA(Pb)) and polyimide (PI(Pb)) were prepared by a two-step polycondensation approach,starting with ABA(Pb) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) as the diamine monomers,2,2-bis[4-(3,4-dicarlxyphenoxy)phenyl]propane dianhydride (BPADA) as the dianhydride monomer in N-methyl-2-pyrrolidinone (NMP) solvent.ABA(Pb),PAA(Pb) and PI(Pb) are fully characterized by Fourier transform infrared (FTIR) spectroscopy,proton nuclear magnetic resonance spectroscopy (1H-NMR) and elemental analysis.X-ray diffraction analysis (XRD),thermogravimetric analysis (TGA),mechanical tests and -ray spectrometry are used to respectively investigate the chemical structure,thermal stability,mechanical property and radiation-proof property of PI(Pb) materials.Compared with pure polyimide material (PI) and PI-Pb(NO3)2 material which is prepared by physically mixing with equal amount of lead element,PI(Pb) material possesses the highest radiation shielding rate and lowest half-value thickness toward radioactive 60Co and 137Cs sources.It demonstrates that PI(Pb) material exhibits the best -ray radiation-proof property.The key reason is that the lead ions are chemically bonded into the polyimide main chain of PI(Pb),which can achieve a high dispersion of lead ions distributed in the matrix.As a result,an increased probability of -ray interacting with lead atoms helps improve the radiation-proof property of PI(Pb) material.In conclusion,PI(Pb) material not only exhibits a good thermal stability and a good mechanical property,but also has the best -ray radiation-proof property,and thus becomes a promising light weight -ray radiation-proof material.关键词：Polyimide;Lead ion;Composite materials;Gamma rays;Radiation proof
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发布时间：2021-03-19 - 摘要：Five half-sandwich rare earth catalysts Cp'Ln(CH2C6H4NMe2-o)2(1:Cp'=C5Me4SiMe3,Ln=Sc;2:Cp'=C9H7,Ln=Sc;3:Cp'=C5H5,Ln=Sc;4:Cp'=C5H5,Ln=Lu;5:Cp'=C5H5,Ln=Y) were synthesized for homo(co)polymerization of isoprene and styrene activated with [Ph3C]B(C6F5)4] in toluene.The isoprene and styrene polymerization activity,stereoselectivity,molecular weight and molecular weight distribution were studied with these catalysts.The C5H5-ligated scandium complex 3 displayed high activity and cis-1,4-selectivity toward isoprene homopolymerization,and moderate activity and atactic selectivity for the styrene homopolymerization simultaneously.By use of this scandium catalyst,the copolymerization of styrene with isoprene was achieved to afford a family of copolymers with high cis-1,4-isoprene content,controlled molecular weight (Mn=3.5104~8.3104) and narrow molecular weight distribution (Mw/Mn=1.71~1.94).The copolymerization activity reach up to 105 g of polymer (mol of Sc)-1 h-1.The styrene/isoprene copolymers were multi-block copolymers with atactic polystyrene blocks,high cis-1,4-isoprene units (91%).The copolymer composition and molecular weight could be easily controlled by changing the feeding ratio of styrene,isoprene and catalyst.关键词：Scandium;Isoprene;Styrene;Copolymerization
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发布时间：2021-03-19 - 摘要：Brownian dynamics was used to simulate the behavior of the different length polymer single-chains through the nanopores at different temperatures and flow rates.The presence of critical flow rate was confirmed.The results showed the translocation probability increased with the decrease of system temperature at the same flow.The loss of conformational entropy caused by the translocation was lower at lower temperatures,and then the critical flow Jc decreased.This might pullthe smaller chains flow through holes easier.The slopes of translocation probability of samples containing different chain lengths versus flow were almost coincided,which meant that the critical flow Jc was irrelevant with the length of polymer chains.The simulation results were all consistent with theoretical prediction.The translocation time of the polymer chain increased linearly with the length of polymer chain under the constant flow rate.Polymer chains were stretched along the x direction of the flow field when they crossed through the nanopores during the translocation process.The stretching stress reached the highest value when half of the single-polymer chain passed the nanopore.This was because the confinement of polymer chain reached the highest at this moment.And the polymer chain in the vertical direction of the flow field had no obvious effect.关键词：Polymer translocation;Critical flow;Translocation time;Brownian dynamics
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发布时间：2021-03-19 - 摘要：The copolymer (AP) of acrylamide,sodium acrylate,cetyl dimethyl ammonium chloride (C16DMAAC) and the copolymer (DP) of acrylamide,methacryloxyethyltrimethyl ammonium chloride and C16DMAAC were synthesized by the radical copolymerization.Then the AP and DP were characterized by infrared spectroscopy and 1H-NMR.At a constant NaCl concentration of 10000 mg/L,AP and DP were blended to form compound solutions to study the synergistic effect and mechanism between AP and DP with opposite charge by viscosity,rheology and fluorescent measurements.The viscosity measurements showed that the apparent viscosity of the compound solution (AP and DP quality ratio of 7 ∶3) was greatly higher than that of the mono-component polymer solutions with the same mass concentration which indicated that a significant effect was existed between the two polymers.The synergistic effect was stronger between AP and DP when pH=6~8.When the concentration of polymer was 2000 mg/L and concentration of NaCl was 15000 mg/L,the apparent viscosity of AP and DP was 19.9 mPa s and 4.2 mPa s,respectively,while the apparent viscosity of compound solution was up to 370.2 mPa s,which demonstrated a strong salt resistance.Comparing the plateau modulus (G0) and characteristic relaxation time (TR) of compound solution with those of the mono-component polymer solutions,it was proved that the number and structural strength of associations of compound solution were higher than those of the mono-component polymer ones.Additionally,comparing I3/I1 and Ie/Im of compound solution with those of the mono-component polymer solutions,it was also proved that the hydrophobic microdomain number of compound solution was higher than that of mono-component polymer solutions.关键词：Ynergistic effect;Apparent viscosity;Salt resistance;The number of associations;Structural strength of associations;Hydrophobic microdomain
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发布时间：2021-03-19 - 摘要：Ethyl cellulose-graft-poly(-caprolactone) (EC-g-PCL) graft copolymers with controllable EC content as drug delivery material were synthesized via ring-opening polymerization in ionic liquid.The maximum molar ratio of [-CL] and [EC] glucose units calculated by 1H-NMR spectrum was 7∶1.The resutls of atomic force microscope (AFM) showed that the surface of EC-g-PCL graft copolymer membrane became rougher with increasing PCL content.The PCL segments in EC-g-PCL graft copolymers could crystallize and the crystallinity gradually decreased with decreasing PCL content.The clear spherulites structure of PCL segments could not be observed in the graft copolymers with PCL content lower than 20% from polarized optical micrographs.However,the banded spherulites of PCL were formed in the graft copolymers with higher PCL contents.The weight losses of copolymer films were all greater than that of pure PCL after degradation for 30 days in PBS solution.Moreover,the weight loss increased from 2.52% to 8.31% with increasing EC content.The introduction of EC chain to PCL promotes the degradation of PCL.The drug release results show that copolymer films with diclofenac have higher values of burst release and cumulative release than PCL.The drug release kinetics for copolymer films could be described by Ritger-Pappas equation:lnQ=0.3846lnt- 1.8538.The mechanism of drug release was Fickian diffusion.However,PCL film shows non-Fickian diffusion or the combination of diffusion and erosion mechanism.关键词：Graft copolymers;Crystallization;Degradation;Drug release
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发布时间：2021-03-19 - 摘要：Different from general polymer solutions,poly(vinyl alcohol) (PVA) aqueous solutions showed distinctive rheological behaviors caused by the hydrogen bonded networks,which include hydrogen bonding between polymer chains and water,intra and inter macromolecular hydrogen bonding.The steady shear curves sof PVA aqueous solutions with the concentration of 10 wt% indicated four regions with increasing shear rate,the first plateau,the first shear thinning region,the second plateau and the second shear thinning region.The experimental results combined with the scaling theory exhibited that the occurrence of the first shear thinning region owed to the inter-macromolecular hydrogen bonding while the arising of the second shear thinning region was due to the disentanglement of PVA chains.The decreasing of viscosity and hydration number of PVA aqueous solutions with introduction of sodium dodecyl sulfate (SDS) also demonstrated the rheological behavior of PVA aqueous solutions in low shear range mainly depended upon the inter-macromolecular hydrogen bonding.In addition,changes in alcoholysis degree and shearing history produced remarkable effect on hydrogen bonded networks,making different rheological responds for PVA aqueous solutions.Since PVA is a semi-crystalline polymer,spinodal decomposition could be observed in PVA aqueous solutions,resulting in the appearance of polymer-rich and polymer-poor phases.The longer aging time benefited the formation of hydrogen bonding and the phase separation of PVA aqueous solutions,causing the increase of viscosity during the shear recovery process upon decreasing shear rate.关键词：Poly(vinyl alcohol);Steady rheological behavior;Hydrogen bonds
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发布时间：2021-03-19 - 摘要：A series of polypeptide-based amphiphilic hybrid copolymers were synthesized via the combination of ring-opening polymerization (ROP) and thiol-yne click reaction.First,poly(ethylene glycol)-block-poly(-propargyl-L-glutamate) (PEG-b-PPLG) diblock copolymers were prepared by ROP using a monoamine terminated poly(ethylene glycol) (PEG-NH2) as the initiator.Subsequently,the PPLG block was modified with a saturated hydrocarbon (1-octanethiol) or a superhydrophobic fluorinated side group (1-mercapto-1H,1H,2H,2H-perfluorooctane) by thiol-yne reaction with high efficiency.The self-assembly behavior of all obtained copolymers in solutions was finely investigated and characterized using Fourier transform infrared (FTIR) spectroscopy,circular dichroism (CD) spectroscopy,dynamic light scattering (DLS) and transmission electron microscopy (TEM).The polypeptide blocks were shown to exhibit -helix conformations,and all copolymers could spontaneously self-assemble into sphere or rodlike micelles in aqueous or organic solution due to the different solubility of the distinct blocks.Such strategy offers a general and efficient way to achieve various amphiphlic hybrid copolymers using simple copolymer precursors,especially for the preparation of functional self-assembly materials with various architectures.Moreover,the self-assemblies of these functional amphiphilic copolypeptides could be easily modulated by tuning the optional macroinitiators and a series of functional thiols.关键词：Polypeptide;Ring-opening polymerization;Click chemistry;Self-assembly
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发布时间：2021-03-19
Research Article
- 摘要：A two-dimensional microscopic model of microcellular polyurethane elastomer (MPUE) was established by using COMSOL MultiphysicsV4.4 of the multiphysics finite element analysis.Based on the same hole size,the effect of the hole density was calculated,as a result,it significantly affects the mechanical properties of the MPUE.In addition,based on the same hole number,the corresponding hole density also affects the mechanical properties of the MPUE.The results indicate that the hole density is important in affecting the mechanical properties of the MPUE.When the hole density is less than 0.4,the stress increases linearly with the increase of the hole density; while when it is greater than 0.5,the stress increases nonlinearly with the increase of the hole density and the toughening effect of the holes are more obvious.In addition,the fluctuation of the hole size makes an increase of the stress,while reducing the variance of the hole size can improve the stability of the mechanical properties of MPUE.关键词：Microcellular polyurethane elastomer;Mechanical property;Finite element simulation
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发布时间：2021-03-19
Research Bulletin
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