THE RING-OPENING POLYMERIZATION OF D,L-LACTIDE WITH ONE COMPONENT RARE EARTH CATALYST

(D, L)-Lactide (LA) was first polymerized with one component of rare earth cata-lysts [Nd(naph)_3, Nd(oct)_3, Nd(O-iPr)3, Nd(AcAc)_3, Y(AcAc)_3, Sm(AcAc)_3, Er(AcAc)_3)]respectively in solution and in melt state. The effects of [Cat]/[LA] molar ratio, solvents,polymerization time, temperature, various rare earth elements and ligands were investi-gated in detail. The results showed that both the conversion of polymerization and themolecular weight (MW) of poly (D, L-Lactide) (PLA) in melt polymerization are higherthan that in solution polymerization, but the polymerization rate in melt was lowr than insolution. The molecular weight distribution (MWD) of PLA is broader with increasing tem-perature. X-ray study indicated that PLA obtained by Nd(AcAc)_3 in melt polymerizationis an amorphous polymer.     

STUDY OF COMPOSITE MEMBRANE OF CELLULOSE ACETATE OR POLYVINYL ALCOHOL BLENDED WITH METHYLMETHACRYLATE-ACRYLIC ACID COPOLYMER FOR PERVAPORATION SEPARATION*

In this paper, methylmethacrylate-acrylic acid MMA-AA hydrophilic and hydrophobic copolymerswere prepared by copolymerization for preparing membrane materials. The composite membrane of celluloseacetate (CA) blended with MMA-AA hydrophobic copolymer was used for the separation of methanol frompentane-methanol mixture. When the methanol concentration was only 1 wt% ,the permeate flux stillmaintained at 350 g/m~2h and separation factor was as big as 800. The composite membrane of PVA(polyvinyl alcohol) blended with MMA-AA hydrophilic copolymer was used for the separation of ethanol-water mixture. The permeate flux was increased to 975 g/m~2h at 74℃ and the separation factor reached 3000at 25℃. The PVA/MMA-AA blended membrane surface modified by ammonia plasma was also investigatedfor separating ethanol-water mixture. Both permeate flux and separation factor of the membrane wasimproved. However, there was no obvious difference of plasma treatment time in the interval of 20～40 min.     

SELECTIVE SEPARATION OF WATER-ETHANOL MIXTURES THROUGH COPOLYMERIC MEMBRANES: Ⅰ. ACRYLIC ACID AND ACRYLONITRILE COPOLYMER AND ITS IONIZED MEMBRANES

The copolymer of acrylic acid and acrylonitrile has been synthesized and pervaporation properties of the copolymeric membranes have been investigated. In order to elucidate the influence of membrane-permeate interaction on the pervaporation of water-ethanol mixtures and to prepare much improved membranes, the membranes have been treated with alkali metal, alkali earth metal and transition metal salt aqueous solutions. The treated membranes (ionized membranes) exhibited higher separation factors than the untreated membranes. The separation factors of various alkali metal cation membranes decreased in the following order : Li~+>Na~+>K~+, and the permeation rates showed an opposite tendency. The dependence of pervaporation behavior on the copolymer composition ,feed concentration and operating temperature have been studied with both ionized and non-ionized membranes. The apparent activation energies of water and ethanol permeation were calculated.     

PERVAPORATION SEPARATION OF ETHANOL-WATER MIXTURES THROUGH PHOSPHATIC POLY(VINYL ALCOHOL)MEMBRANES

制备了以磷酸酯化聚乙烯醇为活性分离层的渗透汽化复合膜并用于乙醇－水混合物的分离。实验结果表明，在进料中乙醇浓度为２０～９５ｗｔ％的范围内，磷酸酯化聚乙烯醇复合膜对乙醇－水混合物中的水均具有很好的渗透选择性，而且，复合膜活性层酯化度对其分离性能具有显著的影响     

PERVAPORATION OF ETHANOL/WATER MIXTURES WITH HIGH FLUX BY ZEOLITE-FILLED PDMS/PVDF COMPOSITE MEMBRANES

Thin-film zeolite-filled silicone/PVDF composite membranes were fabricated by incorporating zeolite particles into PDMS(poly(dimethylsiloxane)) membranes.The morphology of zeolite particles and zeolite filled silicone composite membranes were characterized by SEM.The zeolite-filled PDMS/PVDF composite membranes were applied for the pervaporation of ethanol/water mixtures and showed higher flux compared with that reported in literatures.The effect of zeolite loading and Si/Al ratio of zeolite particles on...     

PREPARATION OF PVA/PAN PERVAPORATION COMPOSITE MEMBRANES AND THEIR SEPARATION PROPERTIES

制备了活性层厚度为１～１０μｍ的ＰＶＡ／ＰＡＮ渗透汽化复合膜并将其用于乙醇水混合物的分离。实验结果表明，热处理条件对复合膜的分离选择性、渗透通量及分离指数具有明显影响。确定了最佳热处理条件。     

~(13)C核磁共振研究稀土催化剂聚合双烯的机理

用~(13)C-NMR 方法测定了稀土顺丁二烯和聚异戊二烯链端结构及序列结构,从链端结构推测的聚合活性链端结构与前文是一致的。在聚异戊二烯中存在着“头-头”和“尾-尾”结构,这种结构引起活性链端甲基位置的改变,从而解释了稀土异戊二烯中3,4-链节的形成。测定了不同聚合温度对聚合物中顺、反结构含量的影响,可用活性链端的 anti-syn异构化加以解释。     

SEPARATION OF PROPANE FROM PROPANE/NITROGEN MIXTURES USING PDMS COMPOSITE MEMBRANES BY VAPOUR PERMEATION

 This study deals with polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) composite membranes for propane separation from propane/nitrogen mixtures, which is relevant to the recovery of propane in petroleum and chemical industry. The surface and cross-section morphology of PDMS/PVDF composite membranes was observed by scanning electron microscope (SEM). The surface morphology of PDMS/PVDF composite membranes is very dense. There are three layers, the thin dense top layer, finger-like porous middle layer and sponge-like under layer in the cross-section SEM image of PDMS/PVDF composite membranes. The effects of the types of cross-linking agents and pressure on the membrane permselectivity were investigated. The permeability of nitrogen was independent of feed pressure. However, the permeability of propane increased with the pressure increasing for all membranes. The membrane cured by a tri-functional crosslinker with attached vinyl groups had better performance than the tetra-functional one, in both selectivity and permeation flux. The total permeation flux is 1.769× 10^-2 cm³(STP)/(cm²·s) and the separation factor is 19.17 when the mole percent of propane in the gas mixture is 10 at the 0.2 MPa pressure difference and 25°C.     

SEPARATION OF PROPANE FROM PROPANE/NITROGEN MIXTURES USING PDMS COMPOSITE MEMBRANES BY VAPOR PERMEATION

This study deals with polydimethylsiloxane(PDMS)/polyvinylidene fluoride(PVDF) composite membranes for propane separation from propane/nitrogen mixtures,which is relevant to the recovery of propane in petroleum and chemical industry.The surface and cross-section morphology of PDMS/PVDF composite membranes was observed by scanning electron microscope(SEM).The surface morphology of PDMS/PVDF composite membranes is very dense.There are three layers,the thin dense top layer,finger-like porous middle layer an...     

NOVEL SYNTHESIS OF POLYARYLENESULFONIUM CATIONS THROUGH A MULTI-ELECTRON TRANSFER PROCESS

The oxidative polymerization of aryl sulfoxides provides a novel polysulfo-nium compound, poly(methylsulfonio-1,4-phenylenethio-1,4-phenylene cation) in quantita-tive yield. The polymerization proceeds efficiently in an acidic solution under atmosphericconditions. Oxygen, chemical and electrochemical oxidations are available. Vanadyl acety-lacetonate and cerium ammonium nitrate act as an effective catalyst for the oxygen ox-idative polymerization. The polymerization mechanism involves multielectron oxidation ofthe sulfides followed by successive electrophilic substitution. The resulting polyarylenesul-fonium cations are useful as a soluble precursor for the synthesis of high molecular weight(M_w>10~5) poly(thio arylne)s.     

FORMATION AND MICROSTRUCTURE OF POLYETHYLENE MICROPOROUS MEMBRANES THROUGH THERMALLY INDUCED PHASE SEPARATION*

Microporous membranes of low-high density polyethylene and their blends were prepared bythermally-induced phase separation of polymer/long-aliphatic chain alcohol (diluent) mixtures.The microstructures of this particular membrane, which depends on the diluent properties,polymer concentration and cooling rate, were observed by scanning electron microscopy."Beehive-type,"leafy-like, and lacy porous structure morphologies can be formed,depending onthe blend composition and phase separation conditions, which were discussed by the polymer anddiluent crystallization processes.     

乙酸稀土盐催化缩聚合成聚(对苯二甲酸乙二酯-co-己二酸乙二酯)

合成了一系列乙酸稀土盐(乙酸钇,乙酸镧,乙酸钕,乙酸镝),作为单组分催化剂,采用熔融缩聚法催化对苯二甲酸二甲酯、乙二醇和1,6-己二酸的共缩聚反应,制备了芳香族脂肪族共聚酯——聚(对苯二甲酸乙二酯-co-己二酸乙二酯)(PETA).通过1H-NMR,SEC,DSC及力学性能测试表征了聚合物的序列结构,分子量及分布,热性能及机械性能.结果表明,乙酸稀土盐单组分可催化共缩聚反应,效果优良,能够合成高分子量和较窄分子量分布的共聚酯,共聚酯具有较高的拉伸强度和断裂伸长率.     

MORPHOLOGICAL CHARACTERIZATION OF POLY (N-VINYLCARBAZOLE) OBTAINED WITH ASYMMETRICALLY STEREOSELECTIVE POLYMERIZATION*

The morphological characterizations of poly(N -vinylcarbazole)(PVCZ) obtained by asymmetricallystereoselective polymerization were studied using x-ray diffraction pattern, DSC and GPC. The results showthat the PVCZs have lower crystallinities (11.0～18.6%) and lower melting heats (2.2～7.5 J/g), but thedegree of crystallinities of the PVCZ samples obtained using the organic salts (acid) with chiral orstereodifferentiating ligands are higher than that using radical and general protonic initiator. It has shown thatthe crystallization is directly related to the packing density of the hexagonal array of the rodlike moleculesformed from the helical chain.     

SURFACE OF GELATIN MODIFIED POLY(L-LACTIC ACID)FILM

In this paper, the surface structure of poly(L-lactic acid) (PLLA) film modified with gelatin was investigated. ThePLLA film specimens were treated directly with aqueous alkali solution to provide their surfaces with carboxyl groups, sothat these functional groups could become the reactive sites for gelatin immobilization. The functional groups of the PLLAfilms were identified by ATR-FTIR spectra and XPS spectra, the changes in surface morphology were observed by usingenvironmental scanning electron microscopy (ESEM), and the hydrophilicity of modified PLLA films was examined bywater contact angle measurement. Experimental results showed that the gelatin was immobilized with water-solublecarbodiimide (EDC) onto the PLLA film's surfaces, and the gelatin content on the polymer surface was related to carboxylicgroup formed in the controlled hydrolysis process. Rough surfaces caused by hydrolysis will predominantly favor the adhesion and growth of cell; and the hydrophilicity of these surfaces after the modification procedure is enhanced.     

CONFORMATIONAL CHARACTERISTICS OF POLY(ACRYLIC ACID) AND POLY(METHACRYLIC ACID)

A full-relaxation optimization of molecule and the Dreiding force field are employed toobtain the geometry parameters and the conformational energy surfaces of meso or racemicdyad of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Three differentcarbonyl-bond orientations of side-groups resulted in the differences in depth of potentialwells in their energetic contours for a meso or a racemic dyad. These discrepancies areinterpreted as a result of various fine structures corresponding to grid search conformationsas well as thereby different interactions. The analysis on the most stable conformationsof PMAA confirmed that the ester groups are nearly perpendicular to the plane definedby the two adjacent skeletal bonds but may possibly change their relative orientations tomeet the requirement of lower energy during the conformational state transition. For eachpolyme, two global energy maps of a meso and a racemic dyad were finally constructedfrom the superposition of energy data for the three kinds of side-group orientations by theBoltzmann factors. From an ensemble average, the proposed scheme with three rotationalisomeric states (RIS) allowed us to access the experimentally unperturbed dimensions ofPAA chain via the configurational statistical mechanics. Although the calculation wasbased on the short-range, local interactions, it was interested to note that the experimentalcharacteristic ratios just fell within the range calculated for atactic chains.     

AN EXTENSION OF THE METHOD FOR PREDICTING PERMEABILITY THROUGH POLYMER MEMBRANES FROM SIMPLE GASES TO WATER VAPOR

It is found that there is a linear relationship between log P_w and the parameter termV_f/0. 5 E_(coh)[1+(δ_w-δ_p)~2/δ_p~2], from the water permeability (P_w) data of 21 polymerscovering 4 orders of magnitude. This correlation may be useful in choosing membranematerials for dehumidification of gases.     

邻羟基苯甲酸希土配合物的合成及晶体结构

本文合成了邻羟基苯甲酸(o-HOC_6H_4CO_2H)与十五种希土的配合物,测定了铈,铽的配合物晶体结构。二者均属单斜晶系,铈配合物空间群为P2_1/n。配位数为9,铽配合物空间群为Cc,配位数为8.两种配合物均呈无限链状聚合结构。     

THEORETICAL ANALYSIS OF KINETICS OF NONISOTHERMAL CRYSTALLIZATION OF POLYMERS

The classical crystallization theories proposed by Avrami, Evans, and Mandelkern wereextended to the nonisothermal situation. The expressions derived from the classical equations canbe expressed in either the differential form or the integral form. A method was provided so as toobtain the parameters characterizing the crystallization rate and mechanism from DSC curves withseveral constant heating or cooling rates. The rate constants of crystallization obtained from bothisothermal and nonisothermal curves of poly(ethylene terephthalate)were compared.     

CONDUCTING BLENDS OF POLY (2-VINYL PYRIDINE) AND POLYETHYLENE OXIDE WITH HIGH MOLECULAR WEIGHT

Ionic, electronic and mixed (ionic-electronic) conductivities of blends of poly(2-vinylpyridine) (P2VP) and poly(ethylene oxide) (PEO) with high molecular weight after dopedwith LiClO_4, TCNQ or LiClO_4 and TCNQ were investigated. Effects of LiClO_4 and TCNQconcentrations on the conductivity of PEO/P2VP/LiClO_4 or TCNQ blend were studied.The ionic conductivity of PEO/P2VP/LiClO_4 blend increases with increasing PEO content.At a Li/ethylene oxide molar ratio of 0.10 and a TCNQ/2-vinyl pyridine molar ratio of 0.5,the mixed conductivity of PEO / P2VP / LiClO_4 / TCNQ is higher than the total of ionicconductivity of PEO/P2VP/LiClO_4 and electronic conductivity of PEO/P2VP/TCNQwhen the weight ratio of PEO and P2VP is 6/4 or 5/5. Scanning electron microscopy(SEM) on the broken cross-section of the PEO/P2VP/LiClO_4 blend and differential scan-ning calorimetry (DSC) results show that LiClO_4 could act as a compatibilizer in the blend.