最新刊期
卷 ， 期 9 ， 2013
- 摘要：Highly filled elastomers are structured three-dimensionally viscoelastic materials formed through interfacial interactions between the rubbery matrix and the fine reinforcing particles such as carbon black and silica.There exist great disputes or contradictory research results about mechanisms of the formation(physical or chemical absorption) of bound rubber(BdR),molecular relaxation of the matrix,reinforcement(Einstein-Smallwood and Guth-Gold equations and their modified forms for isolated particles,dynamic cluster-cluster aggregation model for particle clusters,and rigidity percolation and jamming models for particle network) and nonlinear viscoelasticity(hypotheses in relation to destroying and rebuilding of particle-particle interaction,particle-rubber interaction,particle network and particle-rubber interpenetrating network) of highly filled rubbers in a long time.Nevertheless,the structure and dynamics heterogeneities,strain(strain rate) amplification effect introduced by presence of particles,and the interfacial interactions featured by the presence of a molecular dynamics gradient in the close vicinity around the particles become clear and well-accepted throughout the scientific researches more than one century.On the basis of summarizing some primary results involving influences of BdR on the macroscopic viscoelasticity of rubber materials,the authors propose two important research directions for rubber science in relation to their investigating the viscoelasticity of highly filled rubbers.The first one is to include the structure and dynamics heterogeneities in theories of reinforcement and nonlinear viscoelasticity and the second is to create relationships between microscopic effects(molecular relaxation on different time scales and particle dispersion on different spatial scales) and macroscopic properties for rubber materials via BdR or the particle-rubber gel in filled compounds.关键词：Rubber;Filling;Bound rubber(BdR);Molecular relaxation;Reinforcement;Nonlinear viscoelasticity
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发布时间：2021-03-19
Reviews
- 摘要：In order to prepare vinylidene chloride-methyl acrylate(VDC-MA) copolymer/layered double hydroxide(LDH) nanocomposites with intercalated or exfoliated LDH structure,reversible addition-fragmentation chain transfer living radical polymerization of VDC-MA were carried out in the presence of LDH intercalated with S,S'-bis('-dimethyl--acetic acid)-trithiocarbonate anion groups(CTA-LDH).The structure and properties of CTA-LDH and VDC-MA copolymer/LDH nanocomposites were characterized by Fourier transform infrared spectroscopy,elemental analysis,transmission electron microscopy,gel permeation chromatography and thermogravimetric analysis.It was found that the layer spacing of LDH changed from 0.89 nm to 1.50 nm as CTA anion groups intercalated into LDH through the ion-exchange reaction.The average molecular weight of VDC-MA copolymers was decreased as the amount of intercalated CTA increased,confirming the living nature of VDC-MA copolymerizations.LDH could be gradually exfoliated in the process of in situ RAFT polymerization,and dispersed in VDC-MA copolymer matrix in the form of nanolaminates.The TGA data evidenced that the thermal degradation temperatures of VDC-MA copolymer/LDH nanocomposites were increased as the weight fraction of incorporated LDH increased.关键词：Vinylidene chloride;Layered double hydroxides;Nanocomposite;Reversible addition-fragmentation chain transfer living radical polymerization
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发布时间：2021-03-19 - 摘要：A composite ultrafiltration membrane containing poly(ethylene terephthalate)(PET) non-woven fabric substrate and a PET/PVA composite nanobrous barrier layer based on electrospinning technology and solvent treatment was demonstrated.And this solvent is a mixture of different ratios of acetone and water.The chemical structures of the ultrafiltration membranes surface were characterized in detail by Fourier transform infrared(FTIR) spectroscopy,and surface morphology changes of the top barrier layer after solvent treatment were observed by scanning electron micrograph(SEM).Besides,the influence of the glutaraldehyde(GA) concentration on the hydrolytic resistance of ultrafiltration membrane was also studied.Results reveal that the surface of membranes shows different morphology under the mixed solvent with different ratios of acetone and water,and the optimum proportion of acetone and water was 30/70(by weight); The average diameters of the PET fibers and PVA fibers were about 960 nm and 320 nm,respectively.The optimal hydrolytic resistance(weight loss ratio 2.12% and swelling ratio 3.62%) can be obtained when the dosages of crosslinker was 2 wt%.In addition,the result of FTIR indicated that the hydraxyl amount decreased and the groups such as C=O,COC were introduced to the surface of composite ultrafiltration membrane by cross-linking between PVA and GA.关键词：Electrospinning technology;Ultrafiltration;Nanobrous composite membrane;Hydrolytic resistance
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发布时间：2021-03-19 - 摘要：A series of polyethoxylated amphiphatic palladium catalysts with two-chain polar head have been synthesized and applied in Suzuki polycondensation(SPC),all of which are easy to dissolve in organic solvents for SPC(toluene,THF,DMF) and stable in atmospheric environment.Model polymer poly(9,9-dioctylfluorene)(PFO) with Mn=7104 could be obtained using amphiphatic palladium catalysts with better hydrophilicity(Cp3 and Cm4) in toluene/H2O system,which were comparable to the results with addition of phase-transfer agent(Aliquat 336).As the hydrophilicity of the amphiphatic catalysts got even stronger(Cp4),higher molecular weight(Mn ca. 1105) PFO could be achieved.From the GPC chromatograms for polymerization runs with different amphiphatic catalysts in toluene/water system,amphiphatic catalysts with longer polyethoxyl chain could be used to achieve higher molecular weight.And two peaks could be found in the GPC curves for polymerization runs with amphiphatic catalysts with strong enough hydrophilicity,which means there are high molecular portion and low molecular portion comprising the polymer product,indicating the process might follow two different reaction pathways.One is following the traditional way,base or the boronate anion in water phase are difficult to contact the oxidation addition intermediate in the organic phase,just resulting in low molecular weight polymers.The condition could be improved when the other way followed,the transmetalation step accelerated with the aid of the polyethoxyl chain anchoring to the two-phase interface,the catalytic cycle process could be improved and higher molecular weight polymers could be achieved.The bad performance of these neutral amphiphatic catalysts in THF/H2O and DMF/toluene indicates that the long polyethoxyl chain goes against the oxidation addition step in polar solvents,due to the rather good hydrophilicity of catalysts.关键词：Amphiphatic;Palladium complexes;Polyfluorene;Suzuki polycondensation;Molecular weight
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发布时间：2021-03-19 - 摘要：Using the primary amino-ended polystyrene(PS-NH2) as the macroinitiator,diblock copolymers of polystyrene-b-poly(-benzyl L-glutamate)(PS-b-PBLG) polypeptide hybrids were synthesized by the ring opening polymerization of N-carbonyl anhydride(NCA) method.The molecular weight and its distribution(Mw/Mn=1.4~1.8) were characterized by GPC.Comparing with the first segment,the molar ratios of the compound could be confirmed by 1H-NMR.The thermoproperties characterized by differential scanning calorimetry(DSC) indicate two temperature step changes at 10~20 ℃ and 70~80 ℃,corresponding to the two glass transitions of PBLG and PS,respectively.The texture of PS-b-PBLG in 1,1,2,2-tetrachloroethane(TCE) under a polarizing microscope(POM) shows relatively weak birefringence comparing with that of the PBLG homopolymer,but it still maintains some cholestericliquid crystalline properties.In structure of the shear-oriented solid film,-helical segments were arranged in hexagonal packing,while another larger period parallel to the helical axis was found in small-angle X-ray scattering(SAXS) pattern,indicating a phase-separated structure of alternative lamellar.The morphologies were observed through the transmission scanning electron microscope(TEM).Unlike the zigzag-lamellar texture of films from TCE,the texture of films dried from 1,2-dichloroethane(EDC) is stripe-shaped.The different morphology is due to the solvent effects on the rigidity of -helix,which means the shorter cycle length should be attributed to the -helical folding.It is therefore concluded the self-assembled structure of PS-b-PBLG is changed by the solvents.关键词：Polypeptide hybrids;Rod-Coil diblock copolymers;-helix chain folding;Phase separation;Lamellar structure
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发布时间：2021-03-19 - 摘要：Carbon encapsulated nickel(Ni@C) nanoparticles were synthesized via one step reducing flame spray pyrolysis approach and mixed with HDPE to prepare polymer based positive temperature coefficient(PTC) conductive composites.The as-prepared Ni@C nanoparticles possessed a core/shell structure with carbon shell located outside and nickel core located inside.The mean size of Ni@C nanoparticles was 30~50 nm,and the carbon shell was about 2.9 nm in thickness.The carbon content of Ni@C was about 3.4% calculated from TG analysis.The existence of carbon shell has significantly prevented the agglomeration of metallic nickel particles.Investigations of composite structure were carried by using an optical microscope on slides of composites and section SEM analysis.Results showed the Ni@C had a good spatial distribution in the HDPE matrix,and the PTC conductive composite performed a low percolation threshold of 10 wt% and a high PTC intensity of 8 in magnitude.关键词：Flame spray pyrolysis;Ni@C;PTC performance
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发布时间：2021-03-19 - 摘要：Spherical carbomer resins were synthesized by inverse suspension polymerization,using acrylic acid as monomer,azobi-sisobutryamide chloride(V50) as initiator,sorbitan monstearate(Span 60) and dimethicone copolyol PEG-7 phosphate(DCP) as dispersants,allyl sucrose ether(ASE) and ethoxylated(15) trimethylolprpoane triacrylate(TPET) as crosslinking agent and hexane as continuous organic phase.Nucleation process for the inverse suspension polymerization and the images of the obtained carbomer resin were investigated by optical microscopy and scanning electron microscopy,respectively.The results showed that the polymerization system behaved typical characters of inverse suspension polymerization,and spherical particles of carbomer resin with high bulk density(0.65 g/cm3) could be successfully obtained by the inverse suspension polymerization technique.Also,the study on the polymerization kinetics indicated that the reaction orders of polymerization rate corresponding to monomer concentration and initiator concentration were 0.70 and 1.36,respectively,and the apparent activation energy for polymerization was ca.78.0 kJ/mol.The cross linker amount used in the polymerization system had great effects on the obtained carbomer resin,including viscosity,transmittance,hydrodynamic diameter and shearing resistance of the aqueous solutions.Thickening performance and shearing resistance were enhanced when the carbomer resin was slightly crosslinked with suitable amount of ASE/TPET.关键词：Inverse suspension polymerization;Spherical carbomer resins;Kinetics;Thickening
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发布时间：2021-03-19 - 摘要：To protect the activity of transform growth factor-1(TGF-1),the sulfated chitosan/polylysine/TGF-1(SCS/PLL/TGF-1) nanoparticles were prepared by a co-precipitation method.Along with the increase of sulfated chitosan concentration,the nanoparticles with larger size and more negatively-charged surface were obtained.Both the SCS/PLL and SCS/PLL/TGF-1 nanoparticles had a round morphology observed by transmission electron microscopy(TEM),with a dry size of(17726) nm and(19535) nm,respectively.In vitro cell culture was performed to evaluate the differentiation of bone mesenchyrnal stem cells(BMSCs) induced by the SCS/PLL/TGF-1 nanoparticles.The result of cell proliferation showed that the addition of TGF-1 either in a free state or as nanoparticles could block the proliferation of BMSCs to some extent.However,compared to the blank,SCS/PLL and free TGF-1 groups,the SCS/PLL/TGF-1 group secreted the highest amount of glycosaminoglycans(GAGs).Moreover,the results of quantitative reverse transcription-polymerase chain reaction(qRT-PCR) also showed that the BMSCs seeded with the SCS/PLL/TGF-1 nanoparticles expressed significantly higher amount of collagen type II gene at day 14.All these results confirm that the bioactivity of TGF-1 can be largely preserved in the form of SCS/PLL/TGF-1 nanoparticles,leading to the preferential differentiation of BMSCs toward chondrocytes.关键词：Sulfated chitosan;TGF-1;Nanoparticles;BMSCs;Chondrogenesis
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发布时间：2021-03-19 - 摘要：Bacterial cellulose whisker(BCW) with certain aspect ratio was fabricated by the method of sulphuric acid hydrolysis.It exhibits outstanding monodispersion morphology as shown in the TEM micrographs.The super-absorbent composite resins were prepared by graft copolymers of acrylic acid(AA)/acrylamide(AM) and the hydrated bacterial cellulose whiskers(BCW).The dose of crosslinking agent,free radical initiator,and BCW content was optimized according to Box-Behnken central composite with three factors and three levels response surface methodology.Furthermore,a regression model containing the three factors mentioned above,was constructed where swelling ratio was regarded as the function and the factors as the variables.Swelling behaviors indicated that the resin containing only 0.05 wt% BCW showed the highest water swelling ratio(SR) of 600 gg-1,and also with a good performance in certain saline solution.SEM images showed that the addition of BCW into the resin matrix increased the average-dimension of pores,making it as a porous resin,which illustrated the reason why it may hold more water.FTIR spectroscopy showed that BCW indeed existed in the network of poly(acrylic acid-co-acrylamide) matrix.关键词：Super-absorbent resin;Response surface methodology;Bacterial cellulose whiskers;Water absorbency
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发布时间：2021-03-19 - 摘要：Curing process and curing kinetics of poly{2,5-bis[(4-butyloxyphenyl) oxycarbonyl] styrene/epoxy resin/methyl tetrahydrophthalic anhydride,PBPCS/E-51/MeTHPA,systems were investigated by differential scanning calorimetry(DSC) using the non-isothermal method under different heating rates.Apparent activation energy of the curing systems was calculated by Kissinger method and Ozawa method respectively,and the reaction series were computed by means of Crane formula,then the kinetic equation was concluded.The results indicated that the curing process of the curing reactions followed the first order reaction,and the addition of PBPCS didn't change the curing mechanism of epoxy resin.So mesogen-jacketed liquid crystal polymers could be used for the modification research of epoxy resin.Based on the data of DSC,the optimized curing process of the curing systems is 90 ℃/2h120 ℃/2h140 ℃/1.5h.The results would provide a theoretical basis for curing,performance test and application of PBPCS/E-51/MeTHPA systems,and for epoxy resins modified with mesogen-jacketed liquid crystal polymers.关键词：Epoxy resin;Mesogen-jacked liquid crystal polymer;Cure kinetics;Modify
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发布时间：2021-03-19 - 摘要：A careful comparison on the synergistic flame retardant effect of sodium dodecyl sulfate modified layered double hydroxide(SDS-LDH) and hexadecyl trimethyl ammonium bromide modified montmorillonite(CTAB-MMT) with ammonium polyphosphate(APP) on poly(butyl acrylate-vinyl acetate)(P(BA-VAc)) has been done based on the results of limiting oxygen index(LOI) and vertical burning test(UL-94).P(BA-VAc)/APP/SDS-LDH and P(BA-VAc)/APP/CTAB-MMT owned the highest LOI value at 30.5 and 30.1,respectively,when APP content is 14.5% and layered particle content is 0.5% in flame retardant composites.Thermal degradation behaviors of flame retardant composites were investigated through thermogravimetric analysis(TGA).The amount of char residues of P(BA-VAc)/14.5%APP/0.5%SDS-LDH at 700 ℃ was 2.7 percentage points higher than that of P(BA-VAc)/14.5%APP/0.5%CTAB-MMT.Morphologies and microstructures of residues generated during LOI test were investigated by scanning electron microscopy(SEM).P(BA-VAc)/14.5%APP/0.5%SDS-LDH and P(BA-VAc)/14.5%APP/0.5%CTAB-MMT had more continuous and compact char layer than that of P(BA-VAc)/15%APP.Fourier transform infrared spectroscopy(FTIR),and X-ray photoelectron spectroscopy(XPS) were used to determine the composition of the residues formed by thermal oxidation at 500 ℃.SDS-LDH and CTAB-MMT could promote more esterification and dehydration during the combustion of flame retardant composites.SDS-LDH had a little better synergistic flame retardant effect with APP on char formation.关键词：Ammonium polyphosphate;Vinyl acetate;Butyl acrylate;Flame retardance;Layered inorganic particles
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发布时间：2021-03-19 - 摘要：The strongly basic polymer-supported catalyst containing guanidine functional group has been synthesized.In order not to increase the complexity or cost of the synthetic process,macroporous polystyrene amine resin has been allowed to react nucleophilic addition with cyanamide in situ to generate strong basic guanidine resin from weak basic amine resin designated as PG.PG resin is characterized by FTIR and SEM,and the contents of the strongly basic functional groups bound to the PG resin are determined by acid-base titration and elemental analysis.The effects of pH value,material ratio and reaction temperature on the in situ reaction are also studied.The experimental results show that when pH value of solution is 2,the molar ratio of amine functional groups on the macroporous to cyanamide is 1:3,and reaction temperature is 110 ℃,the strong base exchange capacity is 3.54 mmol/g.The Knoevenagel condensation has been selected to investigate the catalytic activity of the synthesized solid-supported guanidine catalyst.The Knoevenagel condensation is an effective carbon-carbon bond-forming reaction between a carbonyl compound and any compound having an active methylene group.The obtained PG resin has been found to be efficiently catalyze the Knoevenagel condensation reactions with remarkably high yields,and even the reactions of relatively inactive substrates such as ketones can be accomplished at higher temperatures.The effects of the amount of PG resin,reaction solvent and reaction time on the Knoevenagel condensation reactions between benzaldehyde and ethyl cyanoacetate(molar ratio 1:1) are investigated.Optimum reaction conditions are obtained as follows:in ethanol media,reaction time 5 h,n(guanidine functional groups immobilized on the anion exchange resin):n(substrate)=1:5,the yields of 83.1%~95.3% are gained.Lastly,the PG resin has been reused under identical reaction conditions remaining basically the efficiency in catalytic activity at the fifth cycle.关键词：Guanidine;Strong base anion exchange resin;In situ reaction;Knoevenagel condensation
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发布时间：2021-03-19 - 摘要：Polyurethane/poly(methyl methacrylate)/layered double hydroxide(PU/PMMA/LDH) nanocomposites were prepared by means of in situ polymerization with different amounts of the organo-modied LDH.The structure and morphology of nanoparticles were characterized through wide-angle X-ray diffraction(WXRD) and transmission electron microscopy(TEM).The effect of the content of LDH() on the thermal stability and relaxation behavior for PU/PMMA/LDH composites were investigated by using thermogravimetry analysis(TGA),dynamic mechanical analysis(DMA) and broadband dielectric relaxation spectroscopy(BDRS).The results of TGA testing indicated that excellent thermal stability properties of PU/PMMA/LDH nanocomposites could be achieved when the LDH loading() was 0.5 wt%.An exfoliated dispersion of LDH layers in PU/PMMA matrix was varied through the WXRD and TEM observations when was less than 1.0 wt%.Based on the DMA results,it can be found that the maximum of loss factor(tanmax) of PU/PMMA/LDH nanocomposites increased and the glass temperature(Tg) decreased with the increase of .However,when was larger than 1.0 wt%,intercalated LDH layers reduced molecular mobility of polymer matrix and resulted in lower tanmax value and higher Tg than those of pure polymer.Moreover,it has been found by means of BDRS testing that all of relaxation processes for nanocomposites shift to higher temperatures and the relaxation parameter increases with the increase of the LDH loading due to the formation of hydrogen bonding between the surface of LDH and the hard segment of polyurethane.关键词：Polyurethane;Poly(methyl methacrylate);Nano-layered double hydroxide;Morphology;Relaxation
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发布时间：2021-03-19 - 摘要：A novel chelating resin containing quaternary ammonium salt(CPS-DMA-S-HCTA) was synthesized to recycle heavy metals from waste water,and the behavior of adsorption and desorption of Pb(Ⅱ) was discussed.The infared spectra and elemental analysis of the chelating resin showed that CPS-DMA-S-HCTA synthesized successfully.TGA result showed that the initial temperature of decomposition was 205 ℃ and CPS-DMA-S-HCTA was good in thermal stability.The static test showed that the equilibrium adsorption data fitted to Freundlich isotherms.The adsorption is an exothermic process which decreases the confusion and occures spontaneously.The chemical and physical adsorption processes(mainly chemical process) in metal ions adsorption occur concurrently.The best adsorption conditions at 298 K were obtained:the initial concentration of Pb(Ⅱ) was 600 mg/L,pH=5~6,the equilibrium adsorption uptake time was 15 min and the adsorption capacity of Pb(Ⅱ) was 96.1 mg/g.The resin was stable in structural and performance after 10 times of adsorption-desorption-adsorption test,which indicated that the resin can be used repeatedly while more than 98% regeneration efficiency for CPS-DMA-S-HCTA was achieved by using 1.5 mol/L HNO3.关键词：Quaternary ammonium salts;Schiff base chelating resin;5-Cholromethylsalicylaldehyde;Pb(Ⅱ);Adsorption;Desorption
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发布时间：2021-03-19 - 摘要：Porous polyimide(PI) microspheres were prepared using carbon disulfide and ethyl ether as porogens.Porous PI microspheres derived from pyromellitic dianhydride(PMDA) and 4,4'-diaminodiphenyl ether(ODA) were carried out in a non-aqueous emulsion system,in which liquid paraffin was the continuous phase and N,N-dimethylformamide(DMF) was the dispersed phase.The morphologies and chemical structures of the PI porous microspheres were characterized by scanning electron microscopy,quantum chemical simulation,infrared absorption spectroscopy,mercury porosimetry and thermal gravimetric analysis.The results indicated that the morphology of microspheres is good,when carbon disulfide or methanol is used as porogen.However,if carbon disulfide is used as porogen,the number of microsphere pores is small.If methanol is used as porogen,clear pore and porous PI microspheres can be obtained.Hydrogen bonding interaction existing between polyamic acid and ethyl ether plays a critical role in the pore formation process.The pore morphology is mainly controlled through keeping the consistency of curing rate and the evaporation rate.The best porogenic conditions:the temperature of system was 20 ℃,the monomer concentration was 10%,drop speed of pyridine/acetic anhydride was 0.5 s/drop.The specific surface of the porous microspheres is increased with increasing the ratio of ethyl ether/liquid paraffin,which can reach 29.38 m2/g determined with mercury porosimetry.The average particle diameter is about 20~30 m.The resulting samples possess good thermal stability with a decomposition onset temperature of about 517 ℃.关键词：Porous microspheres;Emulsion;Polyimides
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发布时间：2021-03-19
Research Article
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