最新刊期
卷 ， 期 3 ， 2007
- 摘要：Some important results about the injection molding of polyolefin blends were reported in this article.Due to the shear stress and thermal gradients,usually,injection molded parts contain a hierarchy of macromolecular arrangements and a skin-core structure.In this work,the phase morphology and interfacial structure of injection molded bars of polyolefin blends have been investigated in detail from the skin to the core,layer by layer.For preparation of injection-molded bars with high-level orientation dynamic packing injection molding technology was applied to exert oscillatory shear on the molten composite through two pistons that moved reversibly with the same frequency during the solidification stage.It was found that,under the effect of shear stress,(1) the dispersed phase of polymer blends was deformed and oriented,resulting in a change of the phase inversion as well as the mechanical properties of polymer blends;(2) shish-kebab structure instead of spherulite structure was formed;(3) the blends became homogeneous at higher shear stress,while phase separation was induced at lower shear stress;(4) epitaxial growth occurred in injection molded bar of HDPE/iPP blends.Our goal was to study the relationship between processing,morphology and mechanical properties of polymer materials in terms of the morphology controlling and structure characterization of injection-molding samples,and to provide a new way of improving the mechanical properties and service life of polymer materials through injection molding technology.
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发布时间：2021-03-19 - 摘要：Polycarbosilane (PCS) of high molecule weight was a kind of important precursor for SiC fibers with low oxygen content.High molecule weight PCS was synthesized under high pressure by using PCS of low/middle molecule weight synthesized under normal pressure.The structure and performance of the products were characterized by means of FTIR,GPC and NMR measurements.PCS samples of weight overage molecular weight 6400～8500 and less degree of branching were obtained.The suitable conditions for preparation are as follows:reaction time 6 h,Temperature 460～470℃ and pressure 1～2 MPa.
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发布时间：2021-03-19 - 摘要：The effect of fumed silica (SiO2) particles on the phase behavior of poly(methyl methacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN) blends was studied by using small angle laser light scattering (SALLS) and dynamic rheology.The phase diagram of PMMA/SAN blends unfilled and filled with SiO2 particles was obtained.The results revealed that the influence of SiO2 particles on the phase separation behavior of the blend matrix was related to the components of PMMA/SAN blends.Comparing with the 60/40(W/W) PMMA/SAN blends,the addition of a small amount of SiO2 particles could increase the phase-separation temperature (Ts) and could hardly result in the changes of phase separation mechanism,namely,both filled and unfilled blends obeyed the spinodal decomposition mechanism.However,for 30/70 PMMA/SAN blends,the addition of SiO2 particles decreases Ts.This phenomenon was attributed to the component difference between the surface of SiO2 particles and the matrix of PMMA/SAN blends.
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发布时间：2021-03-19 - 摘要：Ultrafine fibers of chitosan/poly(vinyl alcohol) (CS/PVA) were prepared by electrostatic spinning.The effects of solution concentration,mass ratio of CS/PVA and internal diameter of syringe needle on the morphology of ultrafine fibers were investigated by scanning electron microscope (SEM).Furthermore,photocurable monomer triethylene glycol dimethylacrylate (TEGDMA)and photoinitiator 2-hydroxy-2-methyl-1-phenylpropan-1-one were introduced into the CS/PVA blend solution to increase the water-resistance of the fibers,which is a common shortcoming of water soluble polymer fiber.The SEM results showed that,after UV radiation,the water-resistance of fibers was obviously improved by intrafiber-photocrosslinking when the CS/PVA weight ratios is 8∶2 and the concentration of TEGDMA and photoinitiator are 4 wt% and 0.12 wt%,respectively.The average diameter of fibers obtained by this method is around 200 nm.
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发布时间：2021-03-19 - 摘要：A novel end cap 3-trifluoromethyl-4-(phenylethynyl)aniline (3FPA) was obtained by reduction of the corresponding nitro-compound which was synthesized by coupling of 2-trifluoromethyl-4-nitro-1-bromobenzene with ethynylbenzene.Polyimide monomer solutions were prepared by classic PMR process using p-phenylenediamine (p-PDA),the diethyl ester of 4,4′-hexafluoroisopropylidene-bisphthalic acid (6FDE) and 3-trifluoromethyl-4-(phenylethynyl) aniline as endcap.The monomer solution has high solid contents of about 40%～45%,low viscosity of about 28～36 mPa·s and show high stability at room temperature in two months.The polyimide molding powders were produced by thermally curing the monomer solutions at 200℃, and the imidization degree of powders increased with increasing the curing temperature. The thermosetted polyimides were produced by thermal curing the polyimide molding powders at 370℃ under pressure of 1～2 MPa.The postcured polyimide showed a 5% weight loss temperature of 536℃ and Tg about 404℃(DMA).The thermo-oxidative stability of the thermosetted polyimides 3FPA-PI-50 and PMR-Ⅱ resins at elevated temperature (370℃) were determined by isothermally aging the samples in flowing air atmosphere,and the weight loss of 3FPA-PI-50 was about 6.78 wt% after 300 h isothermal aging which was lower than that of PMR-Ⅱ(7.15%).
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发布时间：2021-03-19 - 摘要：The polymerization of styrene (St) with a modified rare earth catalyst system composed of neodymium tricarboxylate (Nd),triisobutyl aluminium (Al) and n-butyl chloride (BCL) was carried out in cyclohexane.The effects of preparation procedure of the catalyst system (the molar ratios of Al/Nd and of BCL/Nd,ageing temperature and ageing time) and reaction conditions (catalyst concentration,polymerization temperature and polymerization time) on St polymerization,catalytic activity,molecular weight and molecular weight distribution of the resultant polymers were investigated.The catalytic activity depended mainly on the molar ratios of Al/Nd and BCL/Nd,the catalyst concentration,the polymerization temperature and time.High molecular weight of polystyrene could be obtained with the catalyst with low Al/Nd and BCL/Nd ratios aged at relatively low temperature for relatively short time.The molecular weight of polymers increased with a decrease in polymerization temperature.The optimum conditions for obtaining high molecular weight polystyrene are as follows:Al/Nd=8～12 (molar ratio),BCL/Nd＝5～25 (molar ratio),Ta＝40～50℃,ta＝6～20 h,Nd/St＝1.5×10-4～6.0×10-4 (molar ratio),Tp＝40～50℃.The molecular weight of the polymers reached high weight-average (Mw) values (Mw=7.6×105 g mol-1) when Al/Nd=10.The molecular weight decreased and molecular weight distribution became broad when excess Al or BCL existed in the catalyst system.The polymer obtained was extracted by 2-butanone and then separated into an insoluble fraction and a soluble fraction.The DSC characterization of the insoluble fraction shows that its melting point is around 268℃,which indicating that the insoluble fraction mainly contains syndiotactic polystyrene.It is shown from polarized optical micrograph that the soluble fraction also contains some segments with high stereo-regularity.
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发布时间：2021-03-19 - 摘要：Cyclodextrins (CD),characterized by their biocompatibility,environmental amity,and low price,have been used in many fields.In recent years,their application in polymer chemistry attracts great attention.In this paper,using styrene as monomer,K2S2O8 as initiator, we investigated the influence of β-CD on the soap-free emulsion polymerization of styrene.It is found that the addition of β-CD can greatly accelerate the polymerization,and increase the monomer conversion.With increase of the amount of CD,the reaction rate also increases.After 5 h,the monomer conversion,in absence of CD,is only 60.3%,which is much lower than that in presence of 1.0 g CD(90%).The final polymer particle-size distribution was more uniform than that without β-CD.The kinetic analysis indicated that β-CD could increase the monomer relative reactivity.AS the ratio of CD/monomer reaches 0.2,the monomer relative reactivity is more than 3 times of that in absence of CD.
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发布时间：2021-03-19 - 摘要：Different types of bore fluids were tested and dimethyl sulfoxide (DMSO) was selected as the optimal bore fluid to eliminate the inner skin.Various concentrations of DMSO in the outside coagulation bath (0～60%) and different coagulation temperature (20～80℃) were used for investigation.The structure of the hollow fiber was examined using scanning electron microscopy (SEM).Thickness of the outer skin decreased with increasing the coagulation temperature.As a result,the membrane flux was enhanced by 2 times as the temperature was increased,while the retention for bovine serum albumin (BSA) and pore size of the membrane did not change significantly.
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发布时间：2021-03-19 - 摘要：The cationic polymerization of isobutylene (IB) by utilizing difunctional initiator dicumyl chloride (DCC) in conjunction with coinitiator AlCl3 was carried out in CH2Cl2/Hex (40/60,V/V) solvent mixtures in the absence or in the presence of 2,6-dimethylpyridine (DMPy) and triphenylamine (TPA) respectively.The effects of concentrations of DCC,electron donor and AlCl3 on monomer conversion,molecular weight and molecular weight distribution (MWD) of the product polyisobutylene (PIB) were investigated systematically.The small amount of water in the polymerization system in conjunction with AlCl3 induced a conventional uncontrolled rapid polymerization of IB and led to polyisobutylene with broad molecular weight distribution.It is found that the GPC trace of resultant polymer obtained by DCC/H2O/AlCl3 system exhibit a bimodal distribution,which was attributed to the competition of initiation from two different active centers,i.e.,H+AlCl3OH- (A) and AlCl4-+C(CH3)2C6H4(CH3)2C+-AlCl4 (B).The initiation from active center (B) increased in the polymerization system with an increase in DCC concentration.A large dosage of DCC (DCC/H2O=5.3) was needed to decrease the initiation from active center (A) effectively,and the polymer with low molecular weight (about 1.8×104) was obtained.According to the characterization results of GPC,NMR and UV,both the initiation efficiency of DCC and molecular weight of polymer increased and MWD narrowed by addition of small amount of TPA or DMPy.The mechanistic role of TPA or DMPy was to decrease the uncontrolled initiation of proton from active center (A) and the chain transfer reaction to monomer.The monomer conversion decreased, but the initiation efficiently increased, and MWD narrowed with increasing of TPA or DMPy concentration.The initiation from active center (A) could be suppressed at high DCC concentration or even at low DCC concentration in the presence of TPA or DMPy.A desirable cationic polymerization of IB would be achieved with DCC/AlCl3 initiation system in the presence of adequate amount of TPA or DMPy, and polyisobutylene with relatively high molecular weight and relatively narrow unimodal molecular weight distribution could be obtained.
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发布时间：2021-03-19 - 摘要：Aromatic diamine 4 containing 2,5-disubstituted pyrimidine structure was synthesized via a condensation reaction of vinamidium salts and amidine chloride salts,followed by hydrazine palladium catalyzed reduction.A series of homo- and co-polyimides containing pyrimidine units were prepared from the diamine and 1,4-phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3,3′,4,4′-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidizaton method.All of the polyimides showed excellent thermal stability and mechanical properties.The glass transition temperatures of the resulting polymides are in the range of 280～437℃, and the 5% weight loss temperatures are in the range of 545～588℃ in air.The polyimides films possess strength at break in the range of 185～282 MPa,elongations at break in the range of 9.1%～51% and tensile modulus in the range of 3.5～6.46 GPa.The polymer films are insoluble in common organic solvents exhibiting high chemical resistance.
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发布时间：2021-03-19 - 摘要：In this paper,a new theoretical way to deduce molcular weight distribution functions in the simple copolymer model is given according to the most probable state using the basic principle in statistical physics for two systems of typical linear copolymers,the forming of which obeys the mechanism of free radical termination by combination and disproportionation.In combination with kinetics principle and probability of the free radical copolymerization,the composition equations i.e. the Mayo-Lowis and the Alfrey-Goldfinger copolymer composition equations are obtained through these distribution functions.This study could help to understand the physical foundation of composition equation in the simple copolymer model and offer at the same time a new method to analyze the free radical copolymerization mechanism.
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发布时间：2021-03-19 - 摘要：A novel approach to in situ crosslinking of copper sulfate (CuSO4)/acrylonitrile-butadiene rubber (NBR) between nitrile groups (—CN) of NBR and copper ions(Cu2+) of CuSO4 was developed.The coordination crosslinking reaction is influenced by many factors,such as the temperature and the time of heat pressing,the —CN content in NBR,the crystal water of metal salts,addition of the plasticizer and etc.The effect of the CuSO4 content on the coordination crosslinking reaction was investigated using X-ray photoelectron spectroscopy (XPS),dynamic mechanical analysis (DMA),differential scanning calorimetry (DSC),equilibrium swelling method and tensile tests.The results show that the extent of coordination crosslinking reaction between CuSO4 and NBR increases with the rise of CuSO4 content.The coordination crosslinked NBR exhibits distinguishing mechanical behavior with increasing the CuSO4 content,from a typical rubber to a ductile and finally to a brittle plastics.Moreover,the scanning electron microscope (SEM) and energy dispersive X-ray spectrum (EDX) results suggested that the coordination crosslinking occurs on the surface of the CuSO4 particles,and the CuSO4 particles not only act as the crosslinking agents,but also the reinforcing inorganic filler in the matrix.These are the essential reasons why the coordination crosslinked CuSO4/NBR exhibits the special and excellent mechanical properties.
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发布时间：2021-03-19 - 摘要：Self-assembled micro/nanotubes of polyaniline (PANI) with a high conductivity (10-2～10-1S/cm) were synthesized by a template-free method in the presence of hydrofluoric acid (HF) as the dopant.The formation probability of PANI-HF micro/nanotubes was nearly 100% when the molar ratio of ［HF］/［An］ was equal to 0.5.The SEM and TEM images revealed that the average diameter of the micro/nanotubes was about 85～420 nm.Besides,it was found that the diameter and conductivity of micro/nanotubes at room-temperature increase with the increase of ［HF］/［An］ ratios.The micro/nanotubes characterized by FTIR and UV-Visible absorption spectrums are identical to the emeraldine salt state of PANI.
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发布时间：2021-03-19 - 摘要：Micro/nano-structures of salicylic acid (SA) doped polyaniline (PANI) deposited on a glass substrate were prepared by a template_free method associated with a deposition process.It is found that the morphology and wettability of the PANI-SA deposited on the substrate are affected by the molar ratio of dopant to aniline (An) and deposition time.A highly hydrophobic surface with a water contact angle of 148°is constructed by the co-existence of microspheres and nanofibers prepared at the reaction time of 60 min and［SA］/［An］= 1∶1. It originates from the contribution of the air trapped in the inter-space of rough surface aggregated by micro/ nano-structures.The molecular structure characterized by FTIR and UV-Visible shows that the product obtained in the initial stage of polymerization is oligoaniline,while the finial product is identical to the emeraldine salt form of PANI.
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发布时间：2021-03-19
Research Article
- 摘要：Multilayer films of a polyacrylate-based azo polyelectrolyte were fabricated by a spin self-assembly method.By spin-coating solutions of the azo polyelectrolyte in DMF/H2O mixed solvent and poly-(diallyldimethylammonium chloride) (PDAC) in water,high quality multilayer films were obtained.Dichroism was optically induced in the self-assembled films under the irradiation of a polarized Ar+ laser beam at 488 nm.The dichroism was easily detected from UV-Vis spectra and exhibited long term stability.The orientational order parameter obtained was about 0.06 for the film.With interfering illumination of Ar+ laser beams,significant surface relief gratings formed on the self-assembled multiplayer films were observed.
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发布时间：2021-03-19 - 摘要：The poly(2,5-dipentyloxy-para-phenylene ethynylene) (P) was synthesized by Pd-catalyzed Sonogashira coupling reaction.Due to causing energy transfer between the nitrobenzene's quenchers and the polymer chains through the charge-transfer interaction,the fluorescence quenched properties of P varied obviously with the para-substituting group's structure in the nitrobenzene derivatives.The fluorescence quenching efficiency of quenchers improved with increasing of electron repulsion capability of the para-substituting group.The fluorescence quenching efficiency increased nonlinearly with the concentration of the quenchers and had,however,no relation with the quenching time.
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发布时间：2021-03-19 - 摘要：The sol-gel transition of aqueous alginate solutions induced by calcium cations has been studied by using dynamic light scattering.A critical relaxation was observed near the gel point,which was characterized by the power law of the time-intensity correlation function g(2)(t)-1∝t-μ.The comparison of this critical exponent μ with the critical exponent n for mechanical relaxation obtained with dynamic rheology measurements shows μ=2n for the Ca-alginate sol-gel transition.The critical exponent μ was found to be proportional to q2,q is the scattering vector,and the proportional coefficient almost equaled to the correlation length of the critical gel.
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发布时间：2021-03-19 - 摘要：Amphiphilic graft copolymers having poly(phthalazinone ether sulfone ketone) (PPESK) backbones and poly(ethylene glycol) side chains were synthesized through a modified Williamson ether method.Initially,chloromethylated PPESK (CMPPESK) was prepared using chloromethylether as chloromethylation agent.Then,PPESK-g-PEGs were synthesized via the coupling of CMPPESK with alkoxides formed from PEG mono methyl ether (PEG-OH) and sodium hydride.Two PEG-OHs with the average molecular weight of 350 g/mol and 750 g/mol,respectively were used as the grafting reactants.The grafting of PEG-OHs onto PPESK backbones was confirmed by FT-IR,1H-NMR and solid 13C CP-MAS NMR.The grafting degrees of PEG-OH were calculated from 1H-NMR analysis,and the obtained results were approximately consistent with those from TGA analysis.The resultant PPESK-g-PEG copolymers were hydrophilic,but water insoluble,rendering them potential candidates as surface modifying additive for PPESK porous membranes.
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发布时间：2021-03-19
Research Bulletin
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