紫精的负离子对耐水的紫精－聚合物膜的光致变色性能的影响

将合不同负离子的苄基紫精分散在混合有ＰＶＰ的ＭＭＡ－ＨＥＭＡ共聚物基质中可制成耐水的光致变色膜。它们的光致变色速度的大小随紫精负离子的不同而有如下序列：这与这些紫精在ＤＭＦ中的溶解度以及在共聚物基质中的溶解性大小的序列相一致．负离子对这些光致变色膜在空气中的氧化退色速度没有很大影响，对这些膜的光疲劳性能的影响也不大。将Ｖ３～Ｖ６分散在不很有ＰＶＰ的ＭＭＡ－ＨＥＭＡ共聚物基质中制成的膜也表现出光致变色的特性，表明它们的多原子负离子本身在聚合物膜中也能充当电子给体的角色．     

甲壳胺药膜的控制释放研究

以阿司匹林为模型药物研究了小分子药物在甲壳腹膜中的释放行为，结果表明释放是扩散控制的，与膜厚、介质pH值，膜交联度及膜分散性密切相关。改变这些参数可达到比较恒定的延长释放和不同的给药途径。     

非甾体类药物含糖乙烯醇酯共聚物制备及药物释放研究

分别利用化学法和酶促法合成了三种药物(萘普生、酮洛芬、布洛芬)乙烯酯和葡萄糖丁二酸乙烯酯(6-O-乙烯丁二酰-D-葡萄糖)两种聚合单体, 通过两种单体的自由基聚合反应制备了具有较高分子量的含糖聚合物前药. 通过IR、NMR对聚合物的结构进行了表征, 用GPC测定共聚物分子量. 含糖聚合物前药的体外释放研究表明, 将小分子原药制备成含糖聚合物前药后, 药物的释放时间大大延长, 达到了缓释的目的. 三种含糖聚合物的药物释放研究表明, 酮洛芬含糖高分子前药的药物释放速率较快, 萘普生含糖高分子前药的药物释放速率较慢. 不同的pH条件下的含糖聚合物的药物释放研究表明, 碱性环境下的药物释放较快, 酸性环境下的药物释放较慢.     

聚乙烯醇衍生的聚离子复合物的研究 Ⅲ．乙烯－乙烯醇共聚物的化学修饰及其复合物

通过化学修饰，在乙烯－乙烯醇共聚物（ＥＶＡ）分子链上分别引入磺酸基、磷酸基或胺基等，制得具有聚离子性质ＥＶＡ衍生物．由这些聚离子复合而形成的聚离于复合物，即使在含水状态也很少失其强度．动态力学性能的测定表明，除了聚离子之间的静电相互作用外，ＥＶＡ中的乙撑链段及共聚物主链的结晶也对维持聚离子复合物的强度有贡献．在水－二甲基甲酰胺一无机强电解质三组分混合溶剂中，与使用ＮａＢｒ或ＵＢｒ的体系比较，聚离子复合物更易溶解于使用Ｃａ（ＳＯＮ）２、ＺｎＯ２或ＮａＳＣＮ的体系．     

聚乙烯醇衍生的聚离子复合物的研究 Ⅲ．乙烯－乙烯醇共聚物的化学修饰及其复合物

通过化学修饰，在惭烯乙烯醇共聚物（ＥＶＡ）分子链上分别引入磺酸基、磷酸基或胺基等，制得具有聚离子性质ＥＶＡ衍生物，由灾些聚离子复合而形成的聚离子复俣，即使在含水状态也很少失其强度 。动态力学性能的测定表明，除聚离子之间物静电相互作用外，ＥＶＡＫ的乙撑链段及共聚物主链的结晶也对维持聚离子复合物的强度有贡献，在水－二甲基甲酰胺－无机强电解质三组分混合溶剂中，与使用ＮａＢｒ蔌ＬｉＢｒ的体系比较。聚离子复     

PVC/PBD-b-PMMA共混体系相容性的研究

采用ＤＭＡ和ＴＥＭ系统研究了聚丁二烯－聚甲基丙烯酸甲酯的嵌段共聚物（ＰＢＤ－ｂ－ＰＭＭＡ）与聚氯乙烯（ＰＶＣ）共混体系的相容性问题。结果表明：ＰＶＣ／ＰＢＤ－ｂ－ＰＭＭＡ共混体系具有部分相溶性。相容的程度与共混体系的组成、组分聚合物的分子量以及共聚物中ＰＢＤ和ＰＭＭＡ嵌段的比例密切相关。     

高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物共混体系的结晶行为

通过ＤＳＣ和ＷＡＸＤ研究了高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物（ＨＤＰＥ／ＬＤＰＥ／ＥＶＡ）三元共混体系的热行为和结晶性能。发现当ＨＤＰＥ含量小于４０％时，ＥＶＡ对ＬＤＰＥ起稀释剂作用，促进ＨＤＰＥ、ＬＤＰＥ的晶相分离，使ＨＤＰＥ、ＬＤＰＥ单独结晶．当ＨＤＰＥ含量高于４０％时，ＬＤＰＥ片晶进入ＨＤＰＥ晶相。形成与ＬＤＰＥ在片晶水平上的共晶。     

LLDPE／EAA共混体系结晶行为及相容性

通过ＤＭＡ、ＤＳＣ、偏光显微镜（ＰＬＭ）、ＷＡＸＤ及力学性能测试等方法，对线性低密度聚乙烯（ＬＬＤＰＥ）／乙烯－丙烯酸共聚物（ＥＡＡ）共混体系的研究表明，ＬＬＤＰＥ与ＥＡＡ的非晶相可部分相容，结晶相不能形成共晶；共混物结晶时，两组分相互影响，ＬＬＤＰＥ的结晶速度高于ＥＡＡ，两者结晶没有进入对方晶胞中．还发现ＬＬＤＰＥ与ＥＡＡ力学性能上相容．低含量ＥＡＡ共混体系显示出较佳的力学性能．     

高密度聚乙烯／低密度聚乙烯／乙烯—醋酸乙烯共聚物共混体系的结晶行为

通过ＤＳＣ和ＷＡＸＤ研究了高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物（ＨＤＰＥ／ＬＤＰＥ／ＥＶＡ）三元共混体系的热行为和结晶性能，发现当ＨＤＰＥ含量小于４０％时，ＥＶＡ对ＬＤＰＥ起稀释剂作用，促进ＨＤＰＥ、ＬＤＰＥ的晶相分离，使ＨＤＰＥ、ＬＤＰＥ单独结晶，当ＨＤＰＥ含量高于４０％时，ＬＤＰＥ片晶入进ＨＤＰＥ晶相，形成与ＬＤＰＥ在片晶水平上的共晶。     

乙烯-乙烯醇共聚物的固体核磁共振研究

乙烯 (Ｅ) /乙烯醇 (Ｖ)共聚物 (ＥＶＯＨ)为结晶性高聚物 ,作为膜材料有着广泛的用途 .在该体系中 ,不仅存在复杂的化学和物理结构 ,如序列分布、立构规整性和共晶结构 ,还存在复杂的氢键相互作用 ,是研究化学结构、聚集态结构和氢键相互作用之间关系的代表性体系 .通过ＤＳＣ[1 ] 、Ｘ 射线衍射[2 ] 、固体高分辨核磁共振碳谱 (1 3Ｃ ＣＰ/ＭＡＳ ＮＭＲ) [3～ 7] 等不同的研究方法 ,前人对ＥＶＯＨ体系及与之直接相关的乙烯醇均聚物(ＰＶＡ)的熔融温度、结晶度以及结晶结构等问题进行了大量研究 .1 984年Ｔｅｒａｏ等[6] 首先报道了在固…     

The effect of copolymerization on transition temperatures of polymeric materials

The relationship between transition temperatures and copolymer composition was studied by DSC. Three types of copolymers were studied: styrene-acrylonitrile (SAN), vinyl chloride-vinyl acetate (VC-VA), and ethylene vinyl acetate (EVA). SAN's and VC-VA's are amorphous copolymers, whereas EVA's are semi-crystalline copolymers. The variation of the glass transitions and the crystalline melting are discussed in this study.     

Kinetic Study of the Accelerating Effect of Coal-burning Additives on the Combustion of Graphite

The relationship between copolymer composition and transition temperatures was studied by means of differential scanning calorimetric analysis and dynamic mechanical spectroscopy. Six samples of ethylene vinyl acetate (EVA) copolymers containing from 5 to 40 mass per cent of vinyl acetate (VA) were studied. The differential scanning calorimetric analysis revealed that each EVA copolymer displays two endothermic peaks (T_m1 and T_m2 ) in the melting zone. Dynamic mechanical spectroscopy was used to determine the primary relaxation temperature (T_α ) for EVA copolymers. This latter characteristic is relatively insensitive to the level of vinyl acetate contained in the copolymer and is influenced by the pulsation frequency ω, also named the angular frequency. This revised version was published online in July 2006 with corrections to the Cover Date.     

Miscibility behavior of ethylene/vinyl acetate and C5 petroleum resin by FTIR imaging.

FTIR microscopic imaging was used to investigate the miscibility behavior of ethylene/vinyl acetate copolymer (EVA) and C5 petroleum resin. Images with an area of 500 x 500 microm(2) were collected in the reflection mode. The miscibility was characterized by probing the spatial distribution of the carbonyl group (C=O) of EVA in the whole images. It was found that a 1:1 hot-melt mixture of EVA and C5 resin showed a good miscibility behavior. For two different EVA copolymers, one with 18% vinyl acetate (VAc) content showed a better miscibility behavior than that with 28% VAc content. Our results demonstrated that this method allowed a direct, convenient and nondestructive visualization. This developed technique promises to become a powerful tool for studying the miscibility behavior of composite materials.     

Non-isothermal crystallization of ethylene-vinyl acetate copolymer containing a high weight fraction of graphene nanosheets and carbon nanotubes

The effect of the different geometrical dimensionality of two dimensional graphene nanosheets(2D GNSs) and one dimensional carbon nanotubes(1D CNTs) on the non-isothermal crystallization of an ethylene-vinyl acetate(EVA) copolymer at high loading(5 wt%) was studied.Transmission electron microscopy indicated a homogeneous dispersion of GNSs and CNTs in EVA obtained by a solution dispersion process.Fourier-transform infrared spectroscopy and differential scanning calorimetry measurements showed that 1D CNTs and 2D GNSs acted as effective nucleating agents,with a noticeably increased onset crystallization temperature of EVA.A high weight fraction of nano-fillers slowed the overall crystallization rate of composites.At the same crystallization temperature,the crystallization behavior of GNS/EVA composites was slowed compared to that of the CNT/EVA ones owing to larger nucleus barrier and activation energy of diffusion.Dynamic mechanical relaxation and rheology behavior of CNT/EVA and GNS/EVA composites demonstrated that the planar structure of the GNSs had an intensively negative effect on EVA chain mobility due to interactions between nanofillers and polymer chains,as well as spatial restriction.     

ASSOCIATION OF ETHYLENE—VINYL ACETATE COPOLYMER IN DILUTE SOLUTIONS Ⅲ. CRITICAL ASSOCIATION CONCENTRATION*

Association behavior of ethylene vinyl acetate (EVA) copolymer in foursolvents 1, 2-dichloroethane (DCE), cyclohexane (CYH), xylene (XYL) and chloroform(CF) has been investigated by dilute solution viscometry The critical association concen-tration (C_A) was determined at which the incipient decrease in slope of the η_(sp)/C～ Ccurve in solutions at the dilute regime. Our results showed that whether the CA couldexist depends on solvent property. The values of CA in DCE increase with increasing, oftemperature and vinyl acetate (VA) content in EVA and decreasing of molecular weight ofEVA.     

Thermodynamic properties of some concentrated polymer solutions

Solubilities of several solvents were measured in four molten polymers by using an isobaric vapor-pressure apparatus. Solvent concentration ranged from 0.5 to 15 wt-%. The systems polyisoprene–benzene and polyisobutylene–benzene were studied at 80.0°C; polyisobutylene–cyclohexane was studied at 100.0°C; ethylene–vinyl acetate copolymer (EVA)–cyclohexane, EVA–isooctane, and poly(vinyl acetate)–isooctane were studied at 110.0°C. Of six polymer–solvent systems studied, all except poly(vinyl acetate)–isooctane appear to exhibit hysteresis in a single sorption–desorption cycle starting with dry polymer. The desorption curves of solvent activity plotted versus solvent weight fraction show an inflection point, suggesting localized adsorption of solvent molecules. Experimental data were analyzed with a theory which takes into account adsorption of solvent by polymer in addition to differences in free volumes and intermolecular forces. The theory gives a semiquantitative representation of the experimental data.     

Evidence of electron acceptor - electron donor interactions in thermoplastic polymer blends by using FTIR - ATR spectroscopy

Specific interactions in binary blends of ethylene/vinyl acetate copolymer (EVA) with various low molecular weight terpene-phenol tackifying resins (TPR) were systematically investigated, as a function of the composition of the blend and of the electron-acceptor ability of the resin, by using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Molecular acid-base were evidenced between TPR hydroxyl groups and EVA carbonyl groups. Quantitative information on the fraction of acid-base bonded entities, the enthalpy and the equilibrium constant of pair formation were obtained. A crystalline transition of the EVA copolymer is observed and is discussed in terms of enthalpy and entropy considerations based on FTIR and calorimetric differential scanning calorimetry (DSC) investigations. Fundamental results are then summarized in order to predict the interfacial reactivity of such polymer blends towards acid or basic substrates.     

Optical properties of polymer blends composed of poly(methyl methacrylate) and ethylene–vinyl acetate copolymer

Optical properties for immiscible polymer blends composed of poly(methyl methacrylate), PMMA, and ethylene–vinyl acetate copolymer (EVA) are studied employing various EVA samples with different vinyl acetate contents. PMMA/EVA shows transparency at room temperature when the difference in refractive index between both phases is small. The light transmittance, however, decreases with increasing the ambient temperature. This phenomenon is attributed to the difference in the volume expansion ratio, leading to the difference in refractive index, between PMMA and EVA. It is found that addition of tricresyl phosphate, TCP, improves the transparency and its temperature dependence. As a result, a ternary PMMA/EVA/TCP blend shows high level of transparency in the wide temperature range, although it has apparent phase separated morphology.     

Effect of vinyl acetate content and electron beam irradiation on the flame retardancy, mechanical and thermal properties of intumescent flame retardant ethylene-vinyl acetate copolymer

Ethylene vinyl acetate copolymer (EVA) flame retarded by ammonium polyphosphate (APP) and pentaerythritol (PER) was cross-linked by electron beam irradiation. The effects of vinyl acetate content and electron beam irradiation on the flame retardancy, mechanical and thermal properties of EVA composites were investigated. The volatilized products of EVA/APP/PER composites were characterized by thermogravimetric analysis/infrared spectrometry. As VA content increased, the volatilized products increased in the second decomposition step, but decreased in the third decomposition step. For all samples, the increase of irradiation dose could improve both the gel content and the Limit Oxygen Index (LOI, the minimum oxygen concentration by volume for maintaining the burning of a material) values of irradiated composites. The mechanical and thermal properties of the irradiated EVA composites were also evidently improved at appropriate irradiation dose as compared with those of unirradiated EVA composites, whereas these properties decrease at higher irradiation dose because of the electron beam irradiation-induced oxidative degradation or chain scission.     

Molecular orientation of EVA chains adsorbed on chemically controlled surfaces: influence of specific interactions

Molecular orientation of ethylene–vinyl acetate (EVA) copolymer nanofilms adsorbed on chemically controlled surfaces is studied. Four EVA copolymers with different contents of vinyl acetate (VA) were spin‐coated onto gold, COOH and NH₂ functionalized substrates in order to study chain behaviour when adsorbed in a quasi‐two‐dimensional system. Polarization‐modulation infrared reflection–absorption spectroscopy (PM‐IRRAS), a very suitable technique to study thin films, was the key to quantitative calculation of EVA chain orientational angles. Acid–base interactions between carbonyl groups of the chain ramification (vinyl acetate units) and the surface functionalities are evidenced on the basis of infrared spectra. Their incidence on the molecular orientation is also discussed. Our results show a quasi‐parallel orientation of EVA main chains with respect to the surface plane for all adsorption substrates. At the same time, orientation changes of the acetate groups are observed when the EVA copolymer is adsorbed onto functionalized substrates, suggesting that acid–base interactions could influence the orientation of these groups. However, these changes are limited and cannot reorient the main chain axis. Moreover, our results show that increasing VA content in the chain does not lead to more carbonyl functions involved in acid–base interactions with the adsorption surface. This fact also will be discussed. Copyright © 2003 John Wiley & Sons, Ltd.