最新刊期
卷 ， 期 2 ， 2007
- 摘要：A series of novel solid-solid phase transition heat storage polyurethanes with various molecular weight PEG based soft segments and MDI-BDO based hard segments were synthesized by two-step solution polymerization.DSC,WAXD were used to study the crystallization of the soft and hard segments,microphase separation,phase transition reversibility and thermal cycling stability of the polyurethanes.The results indicated the crystallizability of soft segment was depressed by the introduction of hard segments in the polyurethane,and the soft segments were not able to crystallize until its average molecular weight was above 2000,and the hard segments were not able to form sufficient domains until its content reaching a certain value,those are the two essential conditions for the polyurethanes having good solid-solid phase transition heat storage properties.In addition,the effects of soft segment content and soft segment molecular weight on heat storage properties of the polyurethanes were also studied.The materials also show great phase transition reversibility and reasonably good stability throughout the cycling process and can be considered as promising phase change materials.
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发布时间：2021-03-19 - 摘要：Monodisperse poly(divinylbenzene-co-acrylonitrile) (poly(DVB-co-AN)) microspheres with active cyano groups on the surface and particle size in the range of 0.45～1.79 μm were prepared by distillation-precipitation polymerization in neat acetonitrile in the absence of any stabilizer or additive without stirring and with benzoylperoxide (BPO) as initiator.The comonomer feed ratio has much effect on the morphology and the size of the resultant polymer particles.The SEM images indicated that the copolymer microspheres have spherical shape with smooth surfaces in monodispersity with AN fraction in comonomer feed from 0 to 0.60.The results demonstrated that more functional cyano groups were successfully incorporated into the outer solvent-swollen gel layer of the resultant polymer microspheres with increase AN fraction in comonomer feed.The distillation of a portion of the solvent out of the reaction system during the polymerization was a key problem to avoid the coagulation and afford monodisperse polymer microspheres for the distillation precipitation copolymerization of DVB and AN in acetonitrile.
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发布时间：2021-03-19 - 摘要：The elastic behaviors of star and linear polymer chains confined in parallel interfaces are investigated using pruned-enriched-rosenbluth method (PERM) based on the self-avoiding walk (SAW) model.The simulation results suggest that if the interfaces have the adsorptive effect on the chains,the accretion of the distance between parallel interfaces D needs acting force; while if the interfaces have no attraction,the accretion of D is a spontaneous process. In our simulation,we calculate the changes of the mean-square radii of gyration 〈S2〉 and the shape factor 〈δ*〉 with D,describing the changes of dimension and shape of the star and linear chains.Additionally,in order to understand the structure and the mechanical behavior in more detail,we also study confined chains of different structure such as train,loop,bridge and tail chains.
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发布时间：2021-03-19 - 摘要：Polyimides containing perfluorocyclobutane rings were synthesized from a new diamine 1,2,3,3,4,4-hexafluoro-1,2-bis(4-aminophenoxy)cyclobutane with three dianhydrides,namely bicyclo［2.2.1］octane-2,3,5,6-tetracarboxylic 2,3,5,6-dianhydride (BHDA),biphenyltetracarboxylic dianhydride (BPDA) and benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA),respectively.The new diamine was synthesized via fluoroalkylation of 4-acetamidophenol with BrCF2CF2Br followed by Zn-mediated elimination and exothermic cyclodimerization.The polymers were characterized by means of FT-IR,inherent viscosity,solubility determination,differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).TGA studies indicated that the polymers were all stable up to 480℃.DSC results show that two of the three polymers have a Tg below 150℃.The polymers were found to be soluble in the commonly used polar solvents.Thus the polymers containing perflurocyclobutane rings exhibited excellent solubility and processability.
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发布时间：2021-03-19 - 摘要：The self-assembled structures of the mixtures of two different diblock copolymers are investigated by self-consistent field theory.In theoretical studies of the present paper, in melts diblock 1 with high degree of polymerization forms lamella and diblock 2 is disorder due to its smaller degree of polymerization.In the mixture systems,for volume fraction of diblock 1 in the range 0.7 ～1.0,lamellar structure occurs.For volume fraction of diblock 1 at 0.4～0.7,cylinder structure occurs.These results are in agreement with some reported experimentally results.Meanwhile,this paper utilizes the monomer density distribution profiles and block junction distribution profiles to analyze the monomer distribution details in the mixture systems.
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发布时间：2021-03-19 - 摘要：High molecular weight polyvinyl acetate (PVAc) with Pn of 1.5×104～2.0×104 and polyvinyl alcohol(PVA) with Pn of 4.1×103～6.6×103 were prepared by mini-emulsion polymerization of vinyl acetate with 2,2′-azobis(2,4_dimethyl valeronitrile) (ADMVN) as initiator,and sodium dodecyl sulfate (SDS)/cetyl alcohol (CA) as surfactant/cosurfactant.PVAc with Pn of 1.5×104～2.0×104 and PVA with Pn of 2.1×103～4.4×103 were also obtained by mini-emulsion with 2,2-azobis(2-amidinopropane)(dihydrochloride） (AAPH) as initiator.The effects of the initiator concentration,temperature and VAc/H2O ratio on molecular weight and conversion were investigated,and the dependence of SDS/CA(mol/mol) ratio on the particle diameter distribution of polyvinyl acetate microspheres and nucleation mechanism was discussed.The stablest mini-emulsion system was obtained at cCA∶cSDS=3∶1. Nucleation occured mostly in monomer droplets regardless of using ADMVN or AAPH as initiator,and the particle diameter distribution of PVAc microspheres with ADMVN as initiator was narrower than the particle diameter distribution with AAPH as initiator.
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发布时间：2021-03-19 - 摘要：The natural rubber (NR)/stytene_butadiene rubber (SBR) based porous polymer membranes were prepared by means of phase-inversion,and the processing parameters and mechanism of membrane_forming were studied systematically.Microstructure of the porous membranes was observed using scanning electronic microscope (SEM) and atomic force microscope (AFM).Abilities of solution uptake and reservation,thermal stability and electrochemical performance were studied as well.Results show that the prepared polymer membranes are porous honeycombing with excellent solution uptake and reservation abilities,the solution uptake ratio is up to 320% and the mass loss is only 31% after heated at 50℃ for 5 h.With that solution uptake ratio,the conductivities arrive 3.93×１０-4 S/cm at ambinet temperature.Electrochemical stability window(4.8 V) and thermal decomposition temperature(157℃) are suitable implying they can be used below 4.8 V and 157℃ safely.The interfacial impedance between membranes and lithium electrodes increase quickly after being kept for 10 days or scanned 20 cycles using cyclic voltammetry,and then,stabilized gradually,showing good interfacial stability which can surpress effectively further growth of solid electrolyte interface (SEI).
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发布时间：2021-03-19 - 摘要：A new method,in which the polymerization of the shell component accompanies the self-assembly of macromolecules,was proposed to prepare core-shell nanospheres.Based on this in situ polymerization method,thermo-sensitive core-shell nanospheres with poly(ε-caprolactone) (PCL) core and poly(N-isopropylacrylamide) (PNIPAM) shell were prepared from monomer NIPAM and crosslinker methylene bisacrylamide (MBA).The influences of the total amount of monomer and crosslinker,the target crosslinking degree of PNIPAM shell,the initial concentration of PCL in DMF and the content of initiator AIBN on the yield of PNIPAM shell,the size,the thermo-sensitive behavior and the morphology of PCL/PNIPAM core-shell nanospheres were studied in details.The results show that during the preparation of PCL/PNIPAM core-shell nanospheres,the polymerization on the surface of PCL nanoparticles competes with that in the water.Increasing the amount of initiator AIBN properly is favorable to the preparation of PCL/PNIPAM core-shell nanospheres with controlled core/shell weight ratio.In addition,the relatively higher reactivity of cross-linker MBA compared with NIPAM leads to the formation of unevenly crosslinked PNIPAM shells.
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发布时间：2021-03-19 - 摘要：The crystallization of poly(vinylidene fluoride) (PVDF) films prepared from dimethylformamide (DMF) and dimethylacetamide (DMAc) solution and subsequently annealed at various temperature was studied by FT-IR and optical microscope.The results indicate that the crystallization of PVDF film depends on solvent,annealing temperature and film thickness.For all samples the content of β phase,F(β),decreases with elevating annealing temperature.When the annealing temperature is less than 90℃,the F(β) of PVDF-DMF system is higher than that of PVDF-DMAc system; however,at 90～160℃,a reversed observation is obtained.For the two systems,interestingly,the F(β) decreases drastically at the region of ca 90℃ and 80℃,respectively.In addition,the crystallization of PVDF is also affected by film thickness,higher film thickness will make the spherulite more resolved.
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发布时间：2021-03-19 - 摘要：A novel hindered amine light stabilizer has been synthesized using 1,2,2,6,6-pentamethyl-4-piperidinol and 4-bromobenzoyl chloride as the raw materials,and has been utilized to end-cap the blue electroluminescent poly-(9,9′-dioctylfluorene).The chemical structure of the polymer has been characterized with nuclear magnetic resonance(1H-NMR) and gel permeation chromatograph (GPC).Its thermo-stability was investigated by comparing the fluorescent spectra after annealing at elevated temperature in air.It clearly demonstrated that the light fluorescent spectroscopic stability of the polymer was greatly improved and the common phenomenon of greenish blue emission has been effectively restrained after end-capped with the hindered amine light stabilizer.
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发布时间：2021-03-19 - 摘要：Effects of silane coupling agent on the dynamic properties for unvulcanized solution-polymerized styrene butadiene rubber (SSBR)/silica (SiO2) compounds were investigated on an advanced rheometric expansion system (ARES).It is found that the molecular structure of silane coupling agent significantly influences the dynamic storage modulus (G′) in the temperature range from 100℃ to 180℃ and also the strain (γ) and frequency (ω) dependence of G′ at 100℃.The highest G′ appears for the compound containing bis-(3-triethoxysilylpropyl)-tetraslufide (TESPT),and the lowest for the compound containing 3-octanoylthio-1-propyltriethoxysilane (NXT),indicating different reaction degrees of silane with SiO2 and SSBR during mixing at 160℃.The molecular structure of silane coupling agents also influences the γ and ω dependence of G′ at 100℃.The critical strains (γc) for the onset of nonlinear viscoelasticity are 1.00%,0.36% and 0.57%,and the slopes of plotting lgG′ versus lgω in the low ωs range (terminal range) are 0.14,0.17 and 0.20,for the compounds containing TESPT,TESPD and NXT,respectively.It is suggested that the increase of both γc value and the slopes of those plots are responsible for surface-modification of SiO2 particles and enhancement of interaction between the particle and SSBR.
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发布时间：2021-03-19 - 摘要：Demonstrated the feasibility of improving mechanical performance of nano-silica/polypropylene (PP) composites by reactive compatibilization.That is,nano-silica particles were grafted by a copolymer of glycidyl methacrylate and butyl acrylate,which were then compounded with PP and the reactive compatibilizer aminated PP.Accordingly,a stronger interfacial adhesion was obtained as characterized by both dynamic mechanical analysis and crystallization behaviors.It helped to give full play to the nanoparticles for toughening and strengthening PP.The factors that influence the graft polymerization and the effect of reactive compatibilization on the properties of nano-silica/PP composites were studied in detail.The results showed that tensile strength,Young's modulus and notch impact strength of PP can be increased at rather low nano-silica contents.
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发布时间：2021-03-19 - 摘要：The selective aggregation of the polyether silicone oil (PSO) on the surface of polystyrene (PS) films was investigated by using the contact angle measurement and the attenuated total reflectance Fourier transform infrared spectroscopy.By utilizing the “surface target" effect of the chain segments of the silicon oil,the applied efficiency of the macromolecular surface modifier(PSO) was enhanced greatly.Because the chain segments of silicone oil could preferential aggregate on the surface of the PSO/PS blends,it led the polyether chain segments migrated on the surface of the films which took the climacteric role in improving the hydrophilicity of the films.It was also found that the preferential surface migration of PSO was heavily depended on the surface properties of the contact medium.Compared with the different mechanisms of the surface migration,the inducement of polar groups on substrates (glass or polyimide) made more chain segments of polyether aggregated on the blends surface, and the polar portion of the surface energy of the films was increased greatly.Whatever the samples were annealed by polyimide or polytetrafluoroethylene,the concentration of silicon chain segments in the surface was much higher than that in bulk.It certified that the “surface target” effect of the silicon oil chain segments was much intensive in the blends.In the process of surface migration,the abundant surface structure was reconstructed.Because the inducement of the polar substrates was attenuated quickly as the operating distance increased,the surface concentration gradient of PSO declined acutely when the samples were annealed on glass or polyimide.But the surface concentration gradient of PSO altered gently when the samples were annealed on polytetrafluoroethylene.
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发布时间：2021-03-19 - 摘要：A grafting copolymer (CPE-g-HEA),composed of poly(2-hydroxy ethyl acrylate) (PHEA) as branched chains and chlorinated polyethylene (CPE) as backbone,was synthesized by in situ chlorinating graft copolymerization.No any initiator was added in the system.The process of in situ chlorinating graft copolymerization comes from continuously introducing chlorine gas into the reaction mixtures composed of only high-density polyethylene powder and a little amount of 2-hydroxy ethyl acrylate (HEA).When heated,a chlorine molecule decomposed into two chlorine radicals,which can lead to chlorination of PE,grafting of HEA to PE and homopolymerization of HEA as well.The structure of CPE-g-HEA was characterized by FT-IR,1H-NMR,GPC and WAXD.The results of FT-IR,1H-NMR and GPC indicated the existence of grafting copolymer of CPE-g-HEA.It can be found that the side chains of the copolymer were very short compared with those of HEA by bulk polymerization according to the GPC trace,and also the copolymer had more branches compared with the aqueous suspension graft system (CPE-g-MMA).
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发布时间：2021-03-19 - 摘要：A series of poly(ethylene glycol) (PEG)-4,4′-diphenylmethanediisocyanate (MDI)-poly(dimethyl-siloxane) (PDMS) multiblock copolymers were synthesized by employing two step growth polymerization technique.Surface phase separation behavior of these multiblock copolymer coatings was studied by atomic force microscopy (AFM) with ultra-light tapping mode.The results showed that nanoscopically well-organized phase-separated surfaces consisting of hydrophilic domains of PEG and MDI segments and hydrophobic domains of PDMS segments were clearly observed even the concentration of PDMS segments in the copolymer was more than 50 wt%,and the microphase separation pattern depended on the annealing,weight fraction of hydrophilic domains or hydrophobic domains and composition of hydrophilic domains.Formation mechanism of surface phase separation was also discussed.
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发布时间：2021-03-19 - 摘要：The kinetics of diethyldiallylammonium chloride (DEDAAC) polymerization and its copolymerization with acrylamide (AM) and acrylic acid (AA) initiated by ammonium persulfate (APS) in aqueous solution was studied by dilatometer method,and the apparent activation energy was measured.In the meantime,the compositions of copolymers of DEDAAC with AM or AA at low conversion were determined by elemental analysis,and the content of chloride ions of the DEDAAC-AM copolymer was determined by chloride ion-selective electrode method,and the reactivity ratios of monomers in copolymerization were obtained by Kelen-Tudos method.The results show that the polymerization rate equation for DEDAAC is RP=k［M］0.99［I］0.76 and the apparent activation energy is 77.00 kJ/mol,which displays that the chain termination reaction is according to the modes of mono- and bi-molecule termination,and the initiating process is independent of monomer concentration.When the monomer feed ratio n(DEDAAC)∶n(AM) is 4∶1,the copolymerization rate equation for DEDAAC with AM is RP=k［M］2.53［I］0.90,the apparent activation energy is 67.06 kJ/mol,and the values of reactivity ratios rDE and rAM are 0.31±0.02 and 5.27±0.53, respectively.While the copolymerization rate equation for DEDAAC with AA is RP=k［M］2.94［I］0.83 at the monomer feed ratio n(DEDAAC)∶n(AA)= 4∶1,the apparent activation energy is 70.07 kJ/mol,and the values of reactivity ratios rDE and rAA are 0.28±0.03 and 5.15±0.28, respectively.The copolymerization for DEDAAC with AM or AA is a non-ideal copolymerization, and the products are random copolymers.
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发布时间：2021-03-19 - 摘要：The carbocationic polymerization of isobutylene (IB) with H2O/TiCl4 as initiating system in the presence of pyridine (Py),triethylamine (TEA) or N,N-dimethylacetamide (DMA) was conducted in a mixture of methylene dichloride (CH2Cl2) and n-hexane (Hex).The effects of solvent polarity,polymerization temperature and monomer concentration on the conversion,molecular weight (MW) and molecular weight distribution (MWD,Mw/Mn) of polyisobutylene (PIB) were investigated.The polymerization rate increased greatly with an increase in solvent polarity.The polymerization rate and the molecular weight of PIB obtained increased obviously with decreasing the polymerization temperature.The corresponding active energy of propagation (ΔE) was calculated to be -28.8 kJ/mol,-25.8 kJ/mol and -29.0 kJ/mol in the presence of Py,DMA and TEA respectively.The chain transfer side-reaction decreased and molecular weight distribution of PIB products became narrow with decreasing polymerization temperature.The polymer with tert-chlorine end group were obtained at -60℃.Both the monomer conversion and molecular weight of PIB increased with isobutylene concentration (［IB］0≤2.5 mol/L) while molecular weight distribution kept relatively narrow and the polydispersity (Mw/Mn) is around 1.4 and 1.5 for the carbocationic polymerization of IB in the presence of Py and TEA respectively.The constant of chain transfer reaction to monomer (CM) was calculated to be 5.5×10-4 and 6.6×10-4 for the carbocationic polymerization of IB in the presence of Py and TEA respectively.A desirable polymerization of IB with apparent absence of chain transfer reactions could be obtained by H2O/TiCl4 initiating system in the presence of Py or DMA at -60℃ under the appropriate reaction conditions.
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发布时间：2021-03-19 - 摘要：The crystallization behaviors of poly(ε-caprolactone) (PCL) in poly(ε-caprolactone) (PCL) and poly-(vinyl methyl ether) (PVME) blends were investigated by POM,DSC,WAXD,SAXS.POM results indicated that spherical crystal morphology was present during isothermal process,and the spheric growth rates were reduced with increasing the contents of PVME in PCL/PVME blends.It was found that the crystallinity of PCL in the blends remained almost constant regardless of the blend composition,but it was dependent on preparation technique.Solution-crystallization was found to be a technique capable of increasing crystallinity levels for some compositions.The melting behavior of the blends is a rather complex process.Both solution-crystallized samples and isothermal-crystallized samples exhibited a single endotherm.Oppositely,melting-crystallized samples exhibited dual-melting endotherms whose mangnitudes vary with blend compositions.On the basis of WAXD and SAXS experiments,it is found that the crystal structure is unchanged,but the long period increases with increasing the content of PVME because of the thickening of the amorphous layers.
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发布时间：2021-03-19 - 摘要：A novel macromolecular surface modifier,a polypropylene-grafted-poly(ethylene glycol) copolymer,was synthesized by coupling of polypropylene containing maleic anhydride with monohydroxyl-terminated poly(ethylene glycol).The effects of reaction conditions on the graft reactions were studied.The copolymers were characterized by IR,1H-NMR,TG and DSC.The results indicated that the graft reactions were hindered by increasing the molecular weight of PP or PEG.The graft copolymer had a lower crystallization capacity as compared with pure PP.The thermal stability of PP-g-PEG decreased with increasing the content of PEG or the molecular weight of PEG.The copolymers were used to blend with polypropylene to modify the surface hydrophilicity of the products.The results of ATR-FTIR showed that PP-g-PEG could diffuse preferably onto the surface of the blends and be suitable as an effectual macromolecular surface modifier for PP.
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发布时间：2021-03-19
Research Article
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