最新刊期
卷 ， 期 3 ， 1999
- 摘要：Molecular dynamics (MD) simulation has been performed on the crystallization process of a single polyethylene chain from fully extended state in the vacuum at different temperatures (100500K with an interval of 100K). The results indicated that each of the simulated crystallization processes consists of three stages. The first stage is a self-cohesion stage, in which the extended chain collapsed to a coil with a sharp decrease of energy and size of the chain. The second stage is an ordering stage in which a lamella was formed by the chain in the way of the adjustment of the chain segments.The last stage is adjusting stage,where the energy and the order keep almost constant,but the lamella shape varies to some extent.Even though there is a big gap in the time scale between MD simulation and laboratory experiments,the fratures of the simulated three stages were very similar to the three stages for bulk polymers in usual crystallization (the nucleation,the crystal gtrowth and the perfection stage).The collapse process of extended chain proceeded via a two-step mechanism at 100K and 500K: a local collapse,forming conpact domains,which subsequently coalesce to yield a fully collapsed state.It was found that the segments in the domains formed in local collapse step were ordered packed at 100K,while the randomly packed at 500K.The self-cohesion rate of the chain is found intensively dependent on the crystallization temperature.The higher temperature resulted in the faster cohesion process.The crystallization temperature also influenced the thickness of the final lamellae.The thicker lamella structure is likely formed at lower temperature.This is different from the crystallization process of polyethylene bulk.
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发布时间：2021-03-19 - 摘要：A new series of the ligands of liquid crystal polymers with T-shaped two-dimensionl mesogens was synthesied by solution condensation polymerization by using 4,4'-(,-alkylenedioyloxy)-dibenzol dichlorids with 2,4-dihydroxy-4]'-alkoxyl azobenzene as the monomers. The low molecular weight compounds were analyzed by elementary analysis, IR, 1H-NMR and MS. The ligands were characterized by GPC,DSC,TG,WAXD and polarizing microscopy with a heating stage. It was found that all the ligand of polymers went to liquid crystal phase when heated to their Tm,the threaded texture ands schlieren texture can be observed.Both Tmand Ti of all the ligands change regulary with the increase of the end alkoxy group length and when the flexible spacer unit in the ligand gets longer.It is worth specially being noted that some of the ligands having no end substituent groups were also found to show liquid crystal behaviors,which would be a new subject for further research on the formation mechanism and the texture of such kind of the ligands.
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发布时间：2021-03-19 - 摘要：The kinetics of isothermal crystallization of nylon 6/montmorillonite nanocomposites with different content of montmorillonite prepared by melt intercalation process has been investigated by DSC.It is shown that the presence of nanometer montmorillonite particles displays a high propensity to nucleate Nylon 6 crystallization,enhance the crystallization rate of Nylon 6,reduce the surface free energies of the developing crystals and improve the behavior of isothermal crystallization of Nylon 6 dealt with the Avrami and Hoffman theories.The crystallization process of Nylon 6 is composed of two stages;the spherulite growth stage and the spherulite nucleation stage.With the increment of the clay content in the Nylon 6/montmorillonite nanoconposites,the crystallization rate parameterk decreases and the surface free energy of the Nylon 6 crystals increases;the spherulite growth stage would become the main stage of the crystallization process in place of the spherulite nucleation stage.
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发布时间：2021-03-19 - 摘要：The kinetics of nonisothermal crystallization of metallocene catalyzed and conventional polyethylenes were studied by differential scanning calorimetry.(DSC) at various scanning rates. The theory of Ozawa and method of Mo Zhishen for nonisothermal crystallization were used to analyze the differntial scanning claorimetry data. As a result of these studies, the Ozawa index of metallocaene catalyzed polyethylene was higher than that of conventional polyethylene. This suggested remarkably different crystallization mechanisms of metallocene catalyzed and conventional polyethylenes,and a higher growth dimension of the former.Moreover,being made by single-site catalytic agent,metallocene catalyzed polyethylene had a higher tacticity of molecular chains than conventional polyethylene.Although metallocene catalyzed polyethylene used in this study had a larger molecular weight,it had a higher rate of crystallization and reached a higher degree of crystallinity.
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发布时间：2021-03-19 - 摘要：During the preparation of polymer dispersed liquid crystalline(PDLC) film from epoxy resin, epichlorohydrin, polyimide and E7, the phase separation process was followed by the chang of transmitance on electro-optical measurement apparatus. It was found that the content of liquid crystal and curing temperature affected the phase separation, and periodic change on the curves of transmittance versus curing time occured. The influences of phase separation process on the electro-optical properties were studied.
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发布时间：2021-03-19 - 摘要：Inverse emulsion copolymerization of acrylaimde (AM) and cationic functional comonomer N,N-dimethyl N-buthyl N-methacrylamidino propyl ammonium bromide was carried out using azobis (isobutylamidine hydrochloride) (AIBA) as initiator. The kinetics of inverse emulsion copolymerization was studied. The effects of the concentration of cationic monomer, emulsifier, initiator and polymerization temperature on polymerization rate (R\-p) were investigated in detail. The kinetic equation Rp=K[DBMPA]1.18[I] 0.75[E]-0.22 was obtained.Moreover,the rheological properties of inverse emulsion were affected by the cationic monomer content,initiator content.etc.
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发布时间：2021-03-19 - 摘要：The reorientation of segments on the copolymer surface with change of immersion mediums have been investigated by dynamic contact angle (DCA) measurements. The samples are amphiphilic copolymer PS-b-PMAA or PS-b-PHPMA prepared by polymerized MAA or HPMA monomer with polystyrene macroinitiatior containing azo group. The results show that the reorientation of polar segments (PMAA or PHPMA segments) on the surface contribute to the contact angle hysteresis. The receding angle θr is very sensityve to polarity and mobility of the segments on copolymer surface while advancing angle θa remains at an approximate value for the samples on which surface PS segment enrichment took place,to the △θ,a differece between advancing angle and receding angle,can be used as an indication of reorientation ability of segments and/or groups on the copolymer surface.The values of advancing angle or of receding angle measured in the second immersion cycle are same as that in the first,respectively,this reveals that the reorientation of segments and/or groups are reversible with the environmental change in the case of both PS-b-PMAA and PS-b-OHOMA.The results also show that the contact angle hysteresis depend on temperature of medium,i.e.,the values of both θ and △θ decrease with increasing of temperature,and that dynamic behavior of the amphiphilic copolymers can be affect by ther ratio of sequence length(MPS/MPMAA/MPHPMA) in the macromolecular chain.
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发布时间：2021-03-19 - 摘要：Isothermal and non-isothermal crystallization kinetics of a syndiotactic polypropylene(sPP) sample synthesized by new metallocene catalyst at different annealing temperatures and different cooling rates have been investigated by using differential scanning calorimetry(DSC) and density analysis.The equilibrium melting temperature(T0m) is 158 by Hoffman-Weeks method.The equilibrium heat of fusion(H0m) is 88J/g in terms of the density analysis and DSC methods. The lateral and end surface free energies derived from the Lauritzon-Hoffman spherulitic growth rate equation are σ=5.2erg/cm2 and σe=69erg/cm2,respectively.The work of chain folding is determined to be q=33.75kJ/mol.Modified Avrami equation and Ozawa equation canbe used to describe the non-isothermal crystallization behavior.And a new and convenient approach by combining the Avrami equation and Ozawa equation in a same crystallinity is used to describe the non-isothermal behavior as well.The crystallization activation energies are evaluated to be 73.7kJ/mol and 73.1kJ/mol for isothermal crystallization and non-isothermal crystallization,respectively.The Avrami exponent nt is 1.5～1.6 for isothermal crystallization procedure,while the Avrami exponent nt,is 2.5～3.5 for non-isothermal crystallization procedure.This indicated the difference of nucleation and growth between the two procedures.
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发布时间：2021-03-19 - 摘要：PET-clay hybrid is a nano composite of PET and uniformly dispersed silicate layers of montmorillonite.Cation exchange capacity of the montmorillonite used in our laboratory is 90 meq./100g.The montmorillonite is a sheet-like particles which are composed of monolayer of 10nm long,10nm wide and 1nm thick.Montmorillonite was dispersed in water or EG,then a kind of nitrogen-onium ion was added to exchange cations between layers of the montmorillonite.Because interlayers were intercalated by onium ion,the interlayer spaces were increased,subsequently the layers of the montmorillonite were delaminated and uniformly dispersed in the solvent.The above treated montmorillonite was mixed with PET oligomer.The mixtures were reacted for 3～4 h at 260 to 280℃,then the PET-clay hybrids were yielded.It is revealed by electron microscopy that the montmorillonite layers are uniformly dispersed at 30～50 nm layer thick in the PET matrix.Crystallization rate of PET-clay is about 4～5 times as quick as that of PET.X-ray patterns of PET-clay hybrids which was quenched at 160℃/min were abtained by WAXD.Crystallinities were calculated by peak resolution method.It is about 53% for quenched PET-clay and much higher than that of pure PET.Neither quenching nor isothermal samples show perfect spherulite structure.It is too small for the size of the spherulite to observe as typical pattern of PET spherulite using polar microscopy and SALS.The montmorillonite layers could act as nucleating agents during crystallization thus increasing crystallization rate,so that molding temperature could be decreased to 60～80℃ during the injection molding.Mechanical and thermal properties of the hybrids were superior to those of PET.The PET-clay hybrids have excellent spinnability.The tensile modulus of the fibers spum by the hybrids is 160% as high as the one of PET fibers.
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发布时间：2021-03-19 - 摘要：The high molecular weight condensation polymers(CEP-1) of dibenzo-18-crown-6(DB-18-C-6) with sebacic acid were good membrane-forming material,which had higher complex selectivities to K+,but the permeabilities of the membranes were low.The permeabilities can be improved greatly when CEP-1 was mixed with a little water-soluble poly(vinyl pyrrolidone)(PVP).The experimental result showed that CEP-1/PVP membranes have high complex rate,complex ability,complex selectivity to K+.The DMA spectra indicated that the modulus[E] and tangent of the loss angle(tanδ),were changed,therefore the CEP-1/PVP blends were partially compatible system.It has been found that the amount of PVP dissolved from CEP-1/PVP membrane were increased with temoerature of water solution raising.
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发布时间：2021-03-19 - 摘要：The liquid crystalline (LC) ordering of nematic mesophase was investigated by measuring the transmitted depolarization light intensity of samples varied with the temperature.The depolarization intensity of a light beam passing through the sample between crossed polarisers increased with temperature during heating,and then it was decreased when the temperature clossed to Ti. The increasing of the depolarization intensity means the growth of LC ordering or domains.This result indicates that the LC ordering in different within temperature range of nematic mesophase.So that the crystallization behavior of samples crystallized from the mesophase melt of different temperatures will be different.The isothermal crystallization from mesophase melt of different LC ordering was determined by DSC.The samples were first melted at different temperature corresponding to different LC ordering for 30 min,and then crystallization was carried out at same temperature to compare their rates.The results obtained indicate that the crystallization rates from mesophase melt of different temperature were quite different for this thermotrpic aromatic polyester.It can be seen from compareison of the data between the depolization light intensity and the crystallization rate that the crystallization rate increases with increasing LC ordering or domain size at first,and then as the LC ordering was decreased the crystallization rate becomes slower when the temperature of mesophase melt close to Ti.These observations could be interpreted that high LC ordering,or large domain size,made it easy to crystallize.
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发布时间：2021-03-19 - 摘要：Four series of konjac glucomannan esters (KGME) of long fatty acid are prepared by heterogeneous method.Differential thermal analysis (DTA) thermographs show the transitions of crystalline structure of KGME.With the increase of degree of substitution (DS) for palmitoylated konjac glucomannan (PKGM), the samples show new crystalline states at higher temperature and the former crystalline state of konjac glucomannan (KGM) disappears.X-ray diffraction spectra indicate the effect of the length of acyl chain on the crystalline structure of KGME.At high DS of octanolylated KGM(OKGM),dodecanolylatedKGM(DKGM),PKGM and octadecenoylated KGM(OLKGM) the intercrystalline distances are 2.10,2.45,2.58 and 3.39nm,respectively,and the effect of DS of KGME on its emulsifying ability has been investigated in aromatic hydrocarbon in water and cycloalkane in water (O/W) emulsions.It is demonstrated that in the proper range of DS.KGME has good emulsifying ability in O/W emulsion,even in high salt concentration and in acidic pH.Clove oil-water (O/W) emulsion has good stability within four weeks at room temperature,and the breakage of emulsion was not brought about.
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发布时间：2021-03-19 - 摘要：Collective single- and few- chain particles of isotactic polystyrene and poly-(ethylene oxide) were obtained by a freeze-drying procedure from dilute solutions.Thermal analysis of the collective particles revealed that cold crystallization temperature depresses,crystallization rate increases and crystal thickening is more evident.These observations can be attributed to none or much fewer entaglements between and within particles.Collective particles crystallized to form small crystals,thus leading to a lower melting temperature.On heating collective particles above equilibrum melting point for a short seriod of time,interpenetration and entanglement occurred and the crystallization and melting behavior characterized by bulk polymer was recovered.
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发布时间：2021-03-19 - 摘要：The thermal degradation of poly(pphenylenebenzobisthiazole) (PBZT) and poly-(pphenylenebenzobisoxazole) (PBZO) was studied by high resolution pyrolysis-gas chromatography/mass spectrometry (HR Py-GC/MS) and thermogravimetry (TG).The pyrorgams of PBZT and PBZO were obtained at the pyrolysis temperatures between 764 and 1040,and the pyrolyzates were identified by on-line MS.The influence of pyrolysis temperature on pyrolyzate yields is discussed.The thermal degradation mechanisms of PBZT and PBZO are described based on the results of HR Py-GC/MS and dynamic parameters.
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发布时间：2021-03-19
Research Article
- 摘要：Easy hydrolytic degradation polyester (EHDPET) is synthesized by esterification polycondensation using terephthalic acid (PTA), isophthalic acid (IPA), poly(ethylene glycol)(PEG), ethylene glycol(EG), and 1,3-di-(2-hydroxyl ethyl) isophthalate 5-sulfonic acid soldium (SIPE). This kind of copolymer is hydrolytic degradable in hot water or NaOH solution. During the synthesis of EHDPET, the melt viscosity is increased with the addition of SIPE, while decreased with the addition of PEG.In contrast with common polyester, the crystalline temperature of EHDPET is higher, at the same time, the melting temperature and glass transition temperature are lower, The hyldrolytic degradation behaviors change with the chemical composition, physical structure, and the hydrolytic conditions of EHDPET. The hydrolytic degradation property is improved by the increase of proportion of SIPE and IPA during the synthesis. The increase of the teperature and the concentration of NaOHsolution also accelerate the hydrolytic degradation. Compared with as-spun fiber, the hydrolytic degradation of the drawn and set fiber decreases.
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发布时间：2021-03-19 - 摘要：In the melt-grafting PP system,the addition of appropriate comonomer could significantly enhance the grafting levels of the grafting monomers and reduce the extent of scission of PP backbone.The criterion of selecting of the appropriate comonomer in PP radical grafting system was discussed. Monomers with different Q and e values were grafted on PP and the Q-e scheme was applied to describe the elationship between those monomers and the comonomer styrene.It was found that the comonomer worked only when the following two conditions were satisfied:The reactivity of the comononer towards PPmacro-radicals mustbe greater than that of the grafting monomer;the Q value of comonomer must be close to that of the grafting monomer. The grafting reaction will be restrained if the Q values between the comonomer and the grafting monomer are greatly different.
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发布时间：2021-03-19 - 摘要：Poly(p-phenylene vinylene)(PPV)and its derivatives have special optoelectronics properties and have aroused great interest in the world as excellent electroluminescent materials up to now.In this paper,a series of soluble PPV derivatives were synthesized by dehydrochlorination reaction with p-methoxy phenol as raw materials.The results showed that attaching the longer alkoxy-substitutes in benzene ring or applying copolymerization could improve the solubility of PPV derivatives and DMSO as a strong polar solvent could increase the yield of polymer. The structure of polymer was indentified by UV/Vis、IR and 1H-NMR.
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发布时间：2021-03-19 - 摘要：A series of blue luminescent materials poly(2, 5-dialkoxyphenylene)(AO-PPP)which were soluble in common organic solvents were prepared by Scholl reaction.The UV-Vis spectrum and photoluminescence(PL)spectrum were studied.The UV-Vis spectrum of AO-PPP exhibit two absorption bands E1 band(short wavelength absorption)and E2 band(long wavelength absorption)which is similar with that of polyphenylene(PPP).The E1 band dont change with increasing of the length of side chain and locates at 242nm,but the E2 band occurs blue shift continuously and splits when the side chain is dodecyloxy ortetradecyloxy. The change of the PL spectrum is also regularly with the increasing of the length of the side chain. The largest emitting peak occur at 400nm when the number of the carbon atom of the side chain equals or is larger than 8.
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发布时间：2021-03-19 - 摘要：Novel types of polysoap hydrogels based on hydrophobically modified polyelectrolytes crosslinked with N, N-methylenebisacrylamide were prepared by free radical polymerization at 70~80℃ in aqueous solution with ammonium persulfate as initiator.The swelling behaviour of the polysoap hydrogels was studied by immersion of the gels in buffered solution at various pHs and ionic strength.It was found that the structure of the polysoap backbone influenced the pH-dependent swelling and deswelling.The swelling process is reversible after repeating cycles of sweeling and deswelling by the change of pH in appropriate buffered solutions.SEM photographs of polysoap gels indicated that the network structures were characterized with regard to an open,large porous and a close,small polous structures in the polysoap hydrogels.
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发布时间：2021-03-19 - 摘要：Two kinds of monomer TPMA and MESDMA containing sulphur,benzene ring and double bond were synthesized,and their structure were characterized By FTIR,1H-NMR and HPLC.Through copolymerizated with Styrene,two kinds of Sulphur-containing transparent optical resins were obtained.The properties of the transparent polymer were shown that copolymerization resins kept good transmitance,and with increasing of TPMA or MESDMA content,the refractive index and density of the optical resin increased linearly.
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发布时间：2021-03-19 - 摘要：Ionic conductivity of a novel predominantly lithium-ion-conducting solid polymer electrolyte is studied. The electrolyte comprises molten lithium salt(s)-acetamide-urea mixtures in which a small amount of an poly(ethylene oxide) is dissolved to stabilized it against recrystallization. The electrolyte has exceptionally hight conductivity at temperature of 70℃ or lower, including ambient temperature, for example 10-3S/cm at 70℃ and 10-4S/cm at 25. The electrolyte combines the best features of the other two,superionic glasselectrolyte and salt-in-polymer electrolyte. Its inoic conductivity depends on the low melting-point eutectic as well as the molecular weight and content of poly(ethylene oxide).
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发布时间：2021-03-19 - 摘要：The influences of the maleic anhydride grafting of ethylene-octene Copolymer elastomer(POE) and the use of modifier (CE-96) on viscosity,isothermal and nonisothermal crystallization kinetics of nylon 6/POE blends were studied by means of capillary rheometer and differential scanning calorimeter.Compared with nylon 6/ungrafted POE blend, the maleic anhydride grafting of POE decreases the crystallization rate and crystallinity,and increases the crystallization size distribution.The addition of CE-96 into nylon 6/POEgMAblends further hinders the crystallization rate and crystallinity of nylon 6 due to the chain extending effect of CE-96 on nylon 6 and the coupling effect at the nylon 6/POEgMA interface.
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发布时间：2021-03-19 - 摘要：An acrylic monomer having βdiketonic moiety,i.e.3-acetyl-5-methyl-5-hexene-2,4-diketone(AMAA) was synthesized by reaction of acetylacetone and methacrylyl chloride in the presence of magnesium ethoxide.It has been found that AMAA is difficult to polymerize by free-radical initiation or heating due to the enol formating of βdiketonic moiety in the monomer.After the protection of the enol form in AMAA by treatment with trimethylsilyl chloride,the free-radical polymerization of AMAA can take place smoothly.The trimethylsilyl group can be removed easily by alcoholysis.It has been revealed by ESR analysis that the carbon atom which connected three strongly electron negative carbonyl groups in AMAA molecule forming a stable carbon free radical lead to retard the propagation during the free-radical polymerization.
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发布时间：2021-03-19
Research Bulletin
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