最新刊期
卷 ， 期 1 ， 2009
- 摘要：The single crystalline ZnO nanowires were self-assembly grown on n-type (111) plane of the silicon substrate using polymer assisted complexing softtemplate process through a simple polymer complexation and lowtemperature oxidizing-sintering,which have smooth top and fine hexagonal columnar structure.Based on the ZnO nanowire/polyacrylamide system,we construct the ZnO nanowire/polyacrylamide light emitting device that exhibits blue electrically driven emission with a relatively low threshold voltage at ambient temperature and pressure,and the ZnO-nanowire-based LED’s emission wavelength is easily tuned by controlling the applied excitation voltage.The nearly vertically aligned ZnO-nanowires with polyacrylamide film were used as emissive layers in the devices.The method uses polyacrylamide as binder in the LED device and dispersion medium in the luminescence layer,which stabilizes the quasi-arrays of ZnO nanowires embedding in a thin polyacrylamide film on silicon substrate and passivates the surface of ZnO nanocrystals,to prevent the quenching of luminescence.The results indicated that the novel technique is a low-cost process for ZnO-based UV or blue light emission and reduces the requirement for achieving robust p-doping of ZnO film.It suggests that such ZnO-nanowire/polyacrylamide-based LEDs will be promising for use in flat-panel displays.
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发布时间：2021-03-19
Rapid Communications
- 摘要：Para-poly(aryl ether sulfone ether ketone ketones) (p-PESEKKs),were prepared by low temperature solution polycondensation of 4,4′-bis(phenoxy)diphenyl sulfone (DPODPS) and terephthaloyl chloride (TPC) in AlCl3/DCE/DMF solvent system.The effects of some factors on solvent induced crystallization behavior of p-PESEKKs were investigated and compared.The results showed that p-PESEKKs of low crystallinity were obtained in the AlCl3/DCE/DMF good solvent system,and they became amorphous after fusion because of the influence of tetrahedral cofiguration of sulfuryl.It was found that the solvent induced crystallization rate and degree of crystallinity decreased with increasing the carbon number of ester end groups,and the end groups with the same structure as the main chain were favorable for crystallization.The high molecular weight p-PESEKKs with lower proportion of end groups were easy to be crystallized by solvent inducement.
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发布时间：2021-03-19 - 摘要：A series of modified polyimides (PIs) exhibiting refractive indices higher than 1.74 were developed by the introduction of sulfur-containing moieties.First,two sulfurheterocyclic-bridged diamines,2,5-bis(4-aminophenylenesulfanyl)thiophene (APST) and 2,5-bis(4-aminophenylenesulfanyl)-1,3,4-thiadiazole (BATT) were synthesized.The two diamines were polymerized with a sulfurcontaining dianhydride 4,4′-［p-thiobis(phenylenesulfanyl)］ diphthalic anhydride (3SDEA) respectively via a two-step polymerization procedure to afford two polyimides (PIs),PI-1 (3SDEA-APST) and PI-2 (3SDEA-BATT).The effects of the sulfur-heterocyclic structure on the properties of the PIs are investigated.It was found that the introduction of the heterocyclic structure decreased the thermal stability and the optical transparency of the PI films to some extent.The initial thermal decomposition temperatures of the PIs are 418℃ for PI-1 and 466℃ for PI-2.The transmittance of the PI films at 450 nm is lower than 50%.However,the sulfur-heterocyclic structure apparently increases the refractive indices of the PI films.The PIs show refractive index of 1.7527 for PI-1 and 1.7490 for PI-2.In addition,the PIs have birefringences lower than 0.01.
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发布时间：2021-03-19 - 摘要：A series of novel-poly(amide-imide)s (PAIs) containing sulfur elements were synthesized and characterized.The flexible sulfur-containing groups,either the linear thioether linkage or cyclic thianthrene group were introduced into the PAIs in order to increase the refractive indices and decrease birefringences of the polymers.Thus,an aromatic diacid compound 1,4-bis(4-trimellit-imidophenylenesulfanyl) benzene (BTPB) was first synthesized from a sulfurcontaining diamine 1,4-bis(4-aminophenylenesulfanyl) benzene (2SPDA) and trimellitic anhydride （TMA）.Then,BTPB was polymerized with two aromatic diamines with high sulfur contents,4,4′-thiobis［(p-phenylenesulfanyl) aniline］ (3SDA) and 2,7-bis(4-aminophenylenesulfanyl)-thianthrene (APTT),respectively to afford two PAIs.The obtained high-molecular-weight PAIs with the inherent viscosities of 1.06～1.17 dL/g are soluble in N-methyl2-pyrrolidinone (NMP) at room temperature.The PAI films exhibit good thermal stability up to 440℃ and glass transition temperatures higher than 190℃.In addition,the PAI films show good optical transparency in the visible light region with the cutoff wavelengths around 400 nm and optical transmittances higher than 90% at 500 nm.The high sulfur contents and the flexible thioether linkages endow the PAI films with refractive indices higher than 1.73 and birefringences lower than 0.04 at 632.8 nm.
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发布时间：2021-03-19 - 摘要：Since the shape memory and recovery characteristics of shape memory polymers (SMPs) are realized by a certain thermalmechanical cycling process,the thermomechanical constitutive equations are critical for predicting the deformation and recovery of this class of materials at different constraint conditions.In this study,a new physical-based,temperature and timedependent constitutive model was proposed.The crystallization theory was used for reference to describe the frozen fraction of SMPs,and the frozen retardant time at the cooling/heating cycle was considered in the constitutive equations.In order to consider both matrix/reinforcement and reinforcement/reinforcement actions during the shape changing process,MoriTanaka approach was used to predict the effective elastic modulus.Moreover,the thermal- and mechanicalfrozen fractions as a function of the temperature were compared.The mechanical strain determines the shape storage characteristics of SMPs and will be frozen mostly at the temperature to be lower than the shape changing temperatures (Ttran) of SMPs.The thermal strain,however,mainly determines the instant recovery stress of SMPs during the shape recovery stage,and the part accumulated at Ttran can hardly be frozen.Hence,the values of the mechanical and thermal frozen fractions at the same temperature are different.Finally,the stress responses at different strain conditions during the cooling process were predicted by the new model,and the results exhibited to be much agreeable with the testing values.
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发布时间：2021-03-19 - 摘要：A series of novel stable polyurethane emulsions with high-solidcontent and low-viscosity were prepared by self-emulsification.They were prepared by the reaction of poly(tetrahydrofuran-co-propylene oxide) glycol(Ng210),isophorone isocyanate（IPDI） with sodium 1,2-dihydroxy-3-propanesulfonate（DHPS） and dimethylolpropanoic acid (DMPA) as hydrophilic chain-extending agents.Influence of the mass ratio of DHPS and DMPA on properties of polyurethane emulsions and films was analyzed.The results showed that the obtained emulsions had multi-modal distribution in particle size, and the particles were spherical in shape.It was noticed that with increasing proportion mass ratio of DHPS and DMPA,the average particles diameter of polyurethane emulsion became smaller and poly-dispersion became wider.In addtion,when the mass ratio of DHPS and DMPA ranges from 4:10 to 6:10,the particle size ratio of big particles and small particle ranges from 6 to 8,the solid-concent of emulsion reaches above 70%,and the volume fraction of big particle ranges from 75% to 80%.It is also noticed that the high-solid-content emulsions exhibit a pseudo-plastic behavior,the apparent viscosity is less than 250 mPa·s (shear rate is 25 s-1).The apparent viscosity of polyurethane emulsion increases with increasing proportion mass ratio of DHPS and DMPA,and the apparent viscosity of emulsion with different solid-content decreases with increasing the shear rate,that is,the emulsions show characteristics of shear thinning.Polyurethane emulsions are endowed lower surface tension which is 41.0～60.0 mN·m-1,and the stability of emulsion is good at high temperatures and low temperatures as well as in storage.When compared to traditional polyurethane emulsions,the emulsions with high-solid-content present films of better mechanical properties.
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发布时间：2021-03-19 - 摘要：Thermally induced phase separation (TIPS) is one of the most important methods to prepare micro-porous polymer membranes.In this paper, isotactic polypropylene (iPP) was dissolved in diamylphthalate (DAP),and the effects of polymer molecular weight on their phase diagram and micro-structure of membranes prepared are studied.Different iPPs and DAP were mixed in a Haake torque rheometer to obtain homogeneous solution.To determine the phase diagram, the cloud points (liquid-liquid phase separation temperatures) and the crystallization temperatures of the iPP/DAP system were examined by microscope with a heating device and DSC,respectively.The micro-structures of the films prepared by TIPS were observed under SEM.The results showed that the liquid-liquid separation temperatures of the solution shifted to higher temperatures when the molecular weight of polypropylene increased.On the other hand, their crystallization temperature curves changed little.These phenomena are interpreted by using Flory-Huggins theory.The molecular weight of polypropylene has a great effect on the resulting average pore size and pore shape in the film via influencing not only the droplet growth time but also the super-cooling temperature range and the coarsening rate.
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发布时间：2021-03-19 - 摘要：Carbon black (CB) filled polypropylene (PP) nanocomposites were prepared by using a mild blending method in the present study.In this compounding process,the CB particles were first dispersed at the nanoscale in aqueous suspension by ultrasonic irradiation.Subsequently,the CB suspension was blended with melting PP using a twin-screw extruder with low shear stress screw configuration,followed by removing the vapor from the vent by vacuum,and the CB particles were located in the PP matrix almost as they were in suspension.The SEM results showed that the CB particles were dispersed at nanometer level in the nanocomposites and distributed homogeneously in PP matrix.The common CB/PP composites had a percolation threshold of about 7.66 vol%,whereas the CB/PP nanocomposites prepared by mild blending method exhibited a very low percolation threshold,i.e.,2.49 vol%.The percolation critical resistivity-exponent t of this nanocomposite was estimated, i.e.,ca. 5.4,which indicated that the system did not obey the prediction of the universal percolation theory.These results were likely attributed to the homogeneous distribution of CB particles,most of which did not contact closely with each other.A conductive model,based on the tunneling conduction theory,was established to simulate and explain these phenomena.The simulation result showed that the relationship between average volume conductivity of the CB/PP nanocomposite and variable （p-pc） deviated from linearity,with the maximum simulated t value as 6.3 Furthermore,it also shared the similar trend with experiment results,indicating that the electrical propertyies of CB/PP nanocomposites prepared by mild blending method were controlled by the percolation tunneling mechanism.
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发布时间：2021-03-19 - 摘要：Sulfonated poly(ether ether ketone)(SPEEK) is a very promising alternative membrane material for direct methanol fuel cells (DMFC).The demand of high proton conductivity calls for the membranes to have a high degree of sulfonation (DS) and work at elevated temperatures.However,with a fairly high DS,SPEEK membrane can swell excessively and even dissolve at high temperatures.To deal with this contradictory situation,phenolphthalein poly(ether sulfone)(PES-C) and sulfonated phenolphthalein poly(ether sulfone)(SPES-C,DS=53.7%) were respectively blended into SPEEK polymer to prepare SPEEK/PES-C and SPEEK/SPES-C blend membranes.DSC results revealed that the two blended polymers showed good miscibility.The effect,that both PES-C and SPES-C can decrease effectively the swelling degree and methanol permeability of blend membranes,became evident with the increment of PES-C and SPES-C contents.Pure SPEEK membrane dissolved completely at 75℃,however,the swelling degree of SPEEK/PES-C（30%）and SPEEK/SPES-C（30%）were 22.5％ and 26.32% at 80℃,respectively.From room temperature to 80℃,the blend membranes presented methanol permeability of around 10-7cm2·s-1,which was about one order of magnitude lower than that of Nafion115.Under 100% relative humidity,the proton conductivity of blend membranes with 20 wt% PES-C exceeded that of Nafion115 above 90℃,the proton conductivity of blend membranes with 30 wt% SPES-C reached 0.11 S·cm-1 of Nafion115 at 110℃.The blend membranes are promising for DMFC application because of their improved applicable temperature,high conductivity and low methanol permeability.
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发布时间：2021-03-19 - 摘要：A new photosensitive polymaleic anhydride terpolymer (P(FM5C-co-MAH-co-St)) was synthesized using radical terpolymerization of maleic anhydride (MAH),styrene (St) and the macromonomer (FM5C,a methacrylate derivate) with a photo-crosslinkable cinnamate pendent.The terpolymer was characterized by GPC,FTIR and 1H-NMR.The self-assembling of the terpolymer was carried out in aqueous solutions.The basic strategy is to form photo-crosslinked colloid particles (PCCPs) by the photodimerization of the cinnamate groups under UV irradiation (300 nm),and then to regulate the morphology of PCCPs by the functional aminolysis reaction between maleic anhydride unit and 2-aminopyridine.It was found that the terpolymic colloid particles (TCPs) would gain a much closer morphology and a more hydrophobic local environment after the photo-crosslinking reaction,and the hydrophilic environment and the average size of PCCPs would increase after the aminolysis regulation.DLS analysis and TEM images showed that TCPs and PCCPs formed well defined solid nano-spheres in aqueous solutions with the average size of 100 nm,but after aminolysis reaction,the average size for PCCPs dramatically increased to about 150 nm.The pyrene probe technique showed that TCPs would gain a much closer morphology and a more hydrophobic local environment after photo-crosslinking with a low I1/I3 (1.40) against the high I1/I3 (1.75) before photocrosslinking reaction,but after aminolysis reaction,the PCCPs expanded and the ratio increased to 1.67.
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发布时间：2021-03-19 - 摘要：Core/shell polyacrylonitrile(PAN)fibers with an outer diameter of 3 μm were prepared by coaxial electrospinning using silicon oil as the core and PAN solution as the shell.After oxidation-stabilized and high-temperature pyrolyzed,some hollow carbon fibers with an outer diameter of 1 μm can be obtained.Morphologies and structural changes of the fibers were characterized by scaning electron microscopy(SEM)and Fouriertransform infrared (FTIR) spectroscopy respectively.Effects of coaxial spinneret and feeding rate ratio of the inner and the outer liquids (Vin/Vout) were studied on the formation of the coaxial fibers.Results showed that the net length of the core nozzle over the shell nozzle,Zp,affected the formation of the coreshell jets greatly:when Zp was about half of the shell nozzle radius (rout),a coaxial jet could be obtained on the tip of the coaxial spinneret; but if Zp increased larger than 0.7 rout,the shell fluid was splitted into multiple jets.In addition,feeding rate ratio also had a great influence.Coaxial fibers could be obtained when Vin/Vout=1,whereas either porous fibers were obtained whenVin/Vout=0.5,or a single PAN solution jet and silicon oil droplets were obtained when Vin/Vout=2.
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发布时间：2021-03-19 - 摘要：In the first step,3-phenylmethyl-2,5-morpholinedione (PMD) was synthesized by using phenylalanine as the raw material.In the second step,poly(lactic acid-co-3-phenylmethyl-2,5-morpholinedione) was prepared by ring-opening copolymerization of PMD and lactide (LA).Stannous octanoate was used as catalyst in the reaction of second step.The structure of copolymers was analyzed by IR,1H-NMRand DSC.The contents of copolymers were detected by infrared spectroscopy instead of 1H-NMR. Two characteristic peaks at 1671.53 cm-1 and 870.82 cm-1-were selected for PMD and PLA in IR.A standard working curve was established:Y=0.05567X+0.1091(r=0.9993),where X was the reciprocal of PMD monomer molar concentration,and Y was the absorbance ratio of PLA to PMD at their characteristic peaks.Effects of catalyst content,reaction time and temperature on the concentration of PMD and ［η］ in copolymers were studied.It was found that,with prolonging of reaction time,the ［η］ was first increased then decreased under the condition of low catalyst concentration.Furthermore,under the condition of high catalyst concentration,the ［η］ suspended during 10 h because of the formation of amide linkage products which are more stable.The concentration of PMD in resulting copolymers increases linerly with the increase of PMD in feed.The PMD was less ring-opening reactive than LA,so it was difficult to incorporate the phenyls into the copolymer.However,under the condition of low feed ratio,the contents of PMD can increase when the temperature becomes higher.Moreover,with increasing the concentration of PMD in copolymer,the influence of catalyst content and temperature on copolymer decreased by the stability of phenyl.
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发布时间：2021-03-19 - 摘要：2,2′-Azobis(2-amidinopropane)dihydrochloride (AIBA) initiator can be efficiently and stably adsorbed onto nanometer silica particles via electrostatic adsorption,and then it can initiate the in situ polymerization of acrylate monomer onto/from the silica particles surface.In order to investigate the activity of adsorbed initiator and the action of adsorbed initiator in the in situ polymerization,the thermal decomposition behaviors of pure AIBA,noadsorbed AIBA and adsorbed AIBA were studied by differential scanning calorimetry (DSC), and the polymerization kinetics of methyl methacrylate (MMA) in in situ emulsion polymerization and in conventional emulsion polymerization was compared by gravimetric method.It was found the thermal decomposition energy of no-adsorbed AIBA and adsorbed AIBA was 148.5 kJ/mol and 124.5 kJ/mol,and their half-life time at 70℃ were 12.6 h and 5.2 h,respectively.All of them implied that the adsorbed AIBA was of higher activity,which finally brought the weakening of the induction period and the improvement of polymerization rate in in situ emulsion polymerization.The anchoring degree and anchoring efficiency of PMMA onto nanosilica particles during in situ emulsion polymerization were further studied by extraction treatment and elemental analysis.It was found that the anchoring of PMMA onto/from silica particles was the dominant means in the early stage.Thus,it is the absorbed AIBA that facilitate the initiation of polymerization on silica surface,which would improve the anchoring of polymer onto/from silica particles and subsequently the composite degree between silica particles and polymer remarkably.
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发布时间：2021-03-19 - 摘要：As there was no report on the degradation properties of poly(p-dioxanone)(PPDO) with molecular weight above 2.0×105, and most studies on PPDO were carried out using monofilament suture of poly(p-dioxanone) as model in previous reports,so it was interesting to study the behavior of PPDO with higher molecular weight in other solid form,such as plates and bars.The in vitro-hydrolytic degradation of high molecular weight poly(p-dioxanone), (Mν＝2.8×105) was studied by the changes of weight retention,water absorption,pH value,intrinsic viscosity,tensile strength,break elongation,thermal properties,crystalline structure and the morphology of PPDO bars in phosphate buffered saline (PBS) (pH 7.44) at 37℃ for 8 weeks.During 8 weeks degradation in PBS,the PPDO samples exhibit obvious changes in their morphology,thermal properties,mechanical properties and degradation behaviors.It was found that the weight loss and water absorption increased slightly,at the same time pH almost maintained original value while the significant decrease of molecular weight was observed.The surface micrographs of PPDO samples showed that microcracks grew with the hydrolytic degradation.The glass transition temperature (Tg) of samples decreased notably,while the degree of crystallinity (Dc) increased and the original crystalline structure substantially remained.The samples lost their tensile strengths and breaking elongation almost completely after 6 weeks of degradation.The results suggested that the PPDO bars with high molecular weight exhibited much smaller degradation rate in vitro hydrolytic degradation.
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发布时间：2021-03-19
Research Article
- 摘要：Narrow-dispersion or monodisperse poly-(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (poly-(GMA-co-EGDMA)) microspheres with stable and smooth surface and particle size in the range of 1.1～3.2 μm were prepared by precipitation polymerization in neat acetonitrile in the absence of any stabilizer and with 2,2′-azobisisobutyronitrile (AIBN) as initiator.The comonomer feed ratio has much effect on the morphology and the size of the resultant polymer particles.As the EGDMA content increased from 20 mol% to 90 mol%,the yield increased from 5.5% to 81.3%,while the particle size had a tendency to decrease with the EGDMA content.The SEM images indicated that the monodisperse microspheres were obtained with EGDMA fraction in comonomer loading from 40 mol% to 70 mol%.The FT-IR spectrum showed the characteristic peaks at 1725～908 cm-1 assigned to the confirmation of the polymerization between GMA and EGDMA.
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发布时间：2021-03-19 - 摘要：Acid-sensitive polymeric micelles have great potential as carriers for target drug delivery systems.In this work,a methacrylate monomer with cyclic orthoester group,(2-ethoxy-5-methyl-1,3-dioxan-5-yl)methyl methacrylate (EDMM),was synthesized.Two acidsensitive amphiphilic block copolymers,PEO-b-PEDMM17 and PEO-b-PEDMM34,were prepared by the atom transfer radical polymerization of EDMM using a PEO macroinitiator (molecular weight ca. 2000 Da).The compositions and molecular weights of the two block copolymers were measured by using 1H-NMR and GPC,respectively.Both polymers are not water soluble due to the hydrophobicity of PEDMM segments.However,micellar aggregates with sizes of 60～200 nm were obtained by slowly adding excessive phosphate buffer (10 mmol/L,pH 7.4) to the polymer solutions in tetrahydrofuran (THF) and then evaporating THF.The micellar aggregates were characterized by dynamic light scattering,transmission electronic microscopy and Nile Red fluorescence probe.PEO-b-PEDMM17,the polymer with a shorter hydrophobic chain length,had a lower critical aggregation concentration(cac) and formed micellar aggregates with smaller size compared with PEO-b-PEDMM34.pH-Dependent hydrolysis of the aggregates were monitored by Nile Red(NR)probe and 1H-NMR approaches,showing that the polymer aggregates were stable at pH 7.4,but the polarity of the micellar core increased with time at pH 5.0 due to the acid-triggered hydrolysis of the orthoester groups.This type of acid sensitive micellar aggregates may find applications as carriers for tumor tissue and/or intracellular drug delivery.
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发布时间：2021-03-19 - 摘要：2-ureido-4［1H］-pyrimidone (Upy) telechelic hyperbranched polymers were prepared and their coating performances were investigated.First,a secondary amine terminated hyperbranched poly(ester-amine) (HPEA) was prepared from piperazine and trimethylolpropanetriacrylate at secondary amine/acrylate group ratio of 2.25/1.At secondary amine/isocyanate stoichiometric ratios of 1∶0.3,1∶0.4 and 1∶0.5,HPEA was further reacted with monoisocyanato methylisocytosine to give three modified hyperbranched polymers bearing terminal Upy units.Based on the 1H-NMR spectra of the modified polymers,the degree of modification was calculated,which agreed well with the feeding composition of the components.Due to the formation of self-complementary quadruple hydrogen bonding of Upy groups,the Upy modified polymers possessed improved glass transition temperature (Tg) and decomposing temperature (Td) compared to HPEA.The coating materials of the modified polymers displayed good mechanical properties.The Tg,Td and coating hardness became higher as increasing the Upy content.All the coatings possessed impact strength of 0.5 kg·m and flexibility of grade 7.This investigation demonstrated that hyperbranched polymers with improved performances could be obtained via incorporating strong hydrogen bonding,which is helpful for designing new dynamic materials.
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发布时间：2021-03-19
Research Bulletin
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