拟合粘度曲线法研究高聚物的长链支化

本文介绍了用计算机试误法拟合粘度曲线,讨论支化参数的方法,本法可以同时确定支化临界分子量和支化程度,在此基础上可以同时得到支化参数及平均分子量、分子量分布.以聚乙烯标准参考物:SRM 1475(线型)、1476(支化物)及镍催化顺式聚丁二烯为对象介绍了上述方法.     

INFLUENCES OF MOLECULAR WEIGHT AND BRANCHING PARAMETER OF LACQUER POLYSACCHARIDE ON THE GROWTH OF LEUCOCYTES

A method of determining branching parameter of lacquer polysaccharide wasestablished by acid-base back-titration of terminal uronic acid of branches. The branchingfactors obtained are in agreement with the values determined by colorimetric method withcarbazole and the results estimated by using Zimm-Stockmayer equation from viscositydata. Influences of molecular weights and branching factors of five fractions of lacquerpolysaccharide on the bioactivities were studied. The results show that the polysaccharideshave bioactivities in motivating the growth of leucocytes, and the effect increases with thedecrease of molecular weight and branching factor in the range studied (17×10~4 >M_w>4×10~4).     

茂金属聚乙烯的非等温结晶行为及其动力学研究

为探索分子量和支链含量对聚乙烯非等温结晶过程的影响,选用3组样品:(1)不同分子量的无支链线形聚乙烯;(2)低分子量的支链含量不同的试样;(3)高分子量的支链含量不同的试样.用DSC研究了这3组样品的非等温结晶动力学.结果表明:(1)与支链含量相比,分子量大小对结晶的影响是次要的,但高分子量样品的结晶度比低分子量样品低;(2)支链对聚乙烯的非等温结晶有重要影响,在支化聚乙烯中起决定作用;(3)无论是高分子量试样还是低分子量试样,支化含量增加,聚乙烯的结晶温度、结晶度、结晶动力学以及晶体的熔点等显著降低.     

双烯化合物类单体合成支化聚合物的支化结构的研究

分别以二乙烯基苯(DVB)、双甲基丙烯酸二缩三乙二醇酯(tri-EGDMA)和1,6-双马来酰亚胺基正己烷(BMIH)为支化单体,采用原子转移自由基聚合合成支化聚苯乙烯;以先核后臂法合成的星状支化聚苯乙烯为参照对合成的支化聚合物的支化形态进行研究.采用气相色谱(GC)、核磁共振氢谱(1H-NMR)和三检测凝胶渗透色谱(TD-SEC)测定了苯乙烯的转化率,聚合物分子量及其分布,特性黏数和均方回转半径.实验结果表明3个支化聚合反应体系内悬垂双键是逐步消耗的,不存在明显的成核过程.反应前期,以形成带有悬垂双键的初级链和轻度支化聚合物为主,聚合物分子量随单体转化率逐步上升;反应后期,悬垂双键聚合导致的分子之间的偶合更加明显,使得聚合物分子量快速上升,合成得到的都是无规支化聚合物.     

用凝胶色谱与毛细管粘度计联用法研究顺丁胶的长链支化

本文讨论了用GPC与自动粘度计联用技术测定高聚物长链支化度的方法,将得到的实测关系[η](V)转化成校准关系[η](V_R)后,利用在同一淋出体积流出支化物和线型分子的([η]·M)乘积相等这一普遍原理,计算出各级分的支化因子g_i、总平均支化因子以及产生支化的临界分子量M~*,并讨论了检测器与粘度计连结管死体积△V及虹吸管残留液对支化参数计算值的影响。     

Inter and intra-molecular branching distribution of tailored LLDPEs inferred by melting and crystallization behavior of narrow fractions

Here we report the melting and isothermal crystallization behavior of two sets of fractions obtained from a film-grade metallocene catalyzed ethylene-1-hexene resin with enhanced mechanical properties. One set of fractions was obtained by molecular weight fractionation, the second set was obtained fractionating by content of 1-hexene. The melting behavior, crystallization kinetics and supermolecular morphology of the fractions are analyzed in reference to the behavior of model systems with uniform inter-chain branching content and a random intra-chain distribution. While melting and crystallization kinetics of molecular weight fractions conforms to the bivariate (molecular weight-comonomer content) distribution of the original copolymer, the behavior of 1-hexene compositional fractions indicate a blockier branching distribution in the highly branched high molar mass fractions. Major differences with model random copolymers are also observed in the supermolecular morphology of the latter fractions.     

分子结构参数对顺丁胶浓溶液流变性质的影响

本工作用GPC-Automatic Viscometer方法测定了顺丁胶样的分子量、分子量分布和支化因子,用同轴圆筒粘度计及落球法测定了顺丁胶浓溶液的粘度,主要研究了分子量分布和长链支化对顺丁胶浓溶液非牛顿流动的影响。提出了描述不同分子量分布的顺丁胶浓溶液粘度的切变速率依赖性的简单公式,并讨论了长链支化对顺丁胶浓溶液非牛顿流动的影响。     

Simulation of degradation processes. II. Testing some relations for random crosslinking without cyclization

By use of a Monte Carlo method the course of crosslinking without cyclization was simulated. For the simulated case the following was determined: number-average molecular weight and degree of polymerization of the system; weight-average molecular weight and degree of polymerization of the system; number of molecules of a given degree of polymerization; quantity of gel; number-average degree of polymerization of sol and branching. The values obtained by simulation were compared with some equations published to date. It was shown that the dependence of weight-average polymerization degree and, consequently, of the weight-average molecular weight on time and the dependence of the number of molecules of a given polymerization degree on time is probably more complicated than hitherto supposed.     

反应温度对聚二甲基硅烷高压合成聚碳硅烷性能的影响

以聚二甲基硅烷(PDMS)为原料,在高压釜内高温高压合成了聚碳硅烷(PCS)先驱体.研究了反应温度对合成的PCS的Si—H键含量、支化度、Si—Si键含量、分子量及其分布、软化点及产率的影响.研究表明,随着反应温度的提高,分子量及软化点均明显增加,分子量分布变宽,支化度升高,Si—Si键含量明显降低.当反应温度低于460℃时,Si—H键含量及产率随反应温度的升高逐渐升高,当反应温度高于460℃时,由于分子间的缩合及热交联二者逐渐降低.在反应过程中PDMS首先转化为小分子量的PCS,然后是小分子PCS分子间发生脱氢及少量脱甲烷缩合使分子量长大.当反应温度高于450℃时,PCS分子量分布出现中分子量峰,Si—Si键含量较低,在室温空气中比较稳定.     

GPC-VIS-MALS study of EVA copolymers: Quantification and interactions of SCB and LCB

Long-chain branching (LCB) is a structural phenomenon that affects important properties in polyethylene (PE) and some copolymers. Quantification of LCB frequency (λ) can be carried out by gel permeation chromatography dotted with detector for viscosity (GPC-VIS) or light scattering (GPC-MALS) by calculating branching indexes against a linear reference. In copolymers, interactions between LCB and SCB (short chain branching) have been described and lead to errors in quantification.In this work, ethyl vinyl acetate (EVA) copolymers of composition ranging 3–20 wt% VA have been studied. A numerical method, developed for the reduction of GPC-VIS and GPC-MALS data of PE, was used for quantifying molecular weights, intrinsic viscosities and gyration radius, as well as the confident ranges. Reliable results were obtained despite the low LCB determined values.A low density polyethylene was also included and compared. Discrepancies in the scaling laws for gyration radius and intrinsic viscosity reveal a strong effect of SCB which was confirmed by the structure factor and its dependence on molecular weight and comonomer content. However, the recently designed gpcBR index revealed to be nearly independent on the short chain branching and allowed detecting differences between apparently similar samples.     

配体骨架烷基取代基对α-二亚胺镍催化乙烯聚合的影响

合成了4种α-二亚胺镍催化剂Ar—NC(R1)C(R2)N—ArNiBr2[Ar=2,6-dimethylphenyl,R1=CnH2n+1,R2=CmH2m+1;其中Cat1:m=1,n=1;Cat2:m=2,n=1;Cat3:m=3,n=1;Cat4:m=2,n=2],考察了聚合温度、催化剂浓度和催化剂配体骨架碳原子上烷基取代基对乙烯聚合反应活性、聚合物链结构和结晶性能的影响.实验发现,当配体骨架上烷基取代基R1和R2不同时,催化剂具有较高的活性,且聚合物分子量也较高;其中,Cat2和Cat3在20℃,乙烯常压和5.8mmol/L催化剂用量下,乙烯聚合活性达1.86×103kgPE/(molNi.h)和1.92×103kgPE/(molNi.h),聚合物分子量(Mw)达6.82×105和1.019×105.聚乙烯链结构分析表明,甲基支链在聚乙烯支链中占主导地位,支化度主要受反应温度的影响;同时还发现,配体骨架碳原子上烷基取代基不同的二亚胺镍催化合成聚乙烯的长支链比例相对较高,特别是在较高反应温度40℃下,己基及以上长支链比例明显增加.     

用GPC-级分特性粘数法表征高顺式-1,4聚丁二烯的长链支化

本文在Ambler方法和kraus方法的基础上,用GPC-级分特性粘数法来测定聚合物的长链支化度,能同时以g_i、λ_i、G_i、m_i、支化重量百分数等支化参数来表征聚合物的支化分布、支化程度和支化含量等;得到了相应的计算gi、λi、[η]_i等有关的计算公式和计算方法;还研制成了以光导纤维为冷光源的高精度光电自动计时毛细管粘度计和60小时内恒温精度优于±5×10~(-4)℃的超级恒温水浴,使计时精度达到≤±4×10~(-3)秒;并以国产和进口的镍系顺丁橡胶为例,讨论了分子量和支化度多分散性之间的某些关系;从而确定了该法比较合理地、全面地相对比较聚合物的长链支化度。     

凝胶化反应全过程的激光光散射跟踪研究

在苯乙烯（Ｓｔ） 二乙烯苯（ＤＶＢ）自由基共聚的凝胶化反应过程中定时取样，得到凝胶化点前后及至终点的一系列样品，然后用激光光散射技术，包括研究散射光强及其角度依赖性的静态光散射（ＳＬＳ）和研究散射光频移的动态光散射（ＤＬＳ），表征了这系列样品的重均分子量Ｍｗ、均方旋转半径Ｒｇ、第二维利系数Ａ２及流体力学半径Ｒｈ等静、动态参量及这些参量的变化规律，定量地描述了凝胶化反应全过程     

Determination of scission, crosslinking and branching parameters of electron beam irradiated methacrylate-acrylamide copolymer

The aim of this work was to investigate the impact of electron beam irradiation at different dose rates on the molecular structure of linear methacrylate-acrylamide copolymer. In the first part, the radiation chemical yields of scission (G_s) and crosslinking (G_x) have been determined after irradiation for various initial molecular weights CL1 (40?000 g/mol), CL2 (90?000 g/mol) and CL3 (425?000 g/mol). Based on this calculation, solvent (ethanol) was found to increase the impact of irradiation especially at low concentration of copolymer. In the second part, the presence of branching in samples before and after e-beam irradiation was explored, and branching calculation was performed.     

红外光谱法研究镍顺丁橡胶分级样品及凝胶的微结构

顺丁橡胶的链结构与其溶液性质和物理性能有密切关系,凝胶的存在往往影响加工和使用性能。付里叶变换红外光谱技术的发展使我们有可能考察顺丁分子链微结构与分子量的关系,研究凝胶与线性分子链结构的差别。     

DETERMINATION OF BRANCHING DISTRIBUTION IN HIGH cis-1,4-POLYBUTADIENE BY GPC AND AUTOMATIC VISCOMETRY

Based on the methods reported by Ambler and Kraus, a method has been developed for the determination of long-chain branching distribution in polymers by the combined use of GPC and intrinsic viscosity data of polymer fractions. In this method, g_i, λ_i, G_i, m_i, the weight percentage of polymer that is branched, etc. can be used simultaneously to characterize the distribution, degree and content of branching in polymers. Some relations between molecular weight polydispersity and branching polydispersity in Nickel-based high cis-1,4-polybutadiene samples are discussed. It was found that the number of long branches λ. per unit molecular weight is a function of molecular weight and all of the samples are highly branched at a molecular weight of about 10~6.     

带支链感光性环氧肉桂酸酯的合成和性能研究

本文对带支链感光性环氧肉桂酸酯的支化度和感光度以及耐溶剂性能之间的关系进行了研究。结果表明,在缠结链的临界分子量以下,随着环氧树脂支化度的增加,环氧肉桂酸脂的感光度和耐溶剂性能都会有较大幅度的提高。     

Cross‐linking emulsion copolymerization of butyl acrylate with diallyl maleate

The emulsion copolymerization of butyl acrylate (BA) with a trifunctional cross‐linker, diallyl maleate (DAM), was investigated. The effect of the monomer feeding time and the amount of cross‐linker on the microstructural properties (branching, cross‐linking, gel formation, and sol MWD) of the seeded semicontinuous emulsion copolymerization of BA with DAM was investigated. It was found that the gel content was not significantly affected by increasing feeding time, but the level of quaternary carbons (an indication of the branching density) increased. On the other hand, increasing the amount of DAM in the feed composition caused gel content, level of quaternary carbons, and the cross‐linking density to increase. Interestingly, the level of quaternary carbons and the cross‐linking density sharply increased during the cooking period. The molecular weight of the sol decreased as DAM increased in the feed. In addition, the effect of process type, batch versus semibatch, was also considered and important differences in the level of quaternary carbons, cross‐linking, and gel content were found. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4684–4694, 2005     

聚乙酸乙烯酯的溶液性质及长链支化度

用粘度法,GPC和LALLS测定了线型及不同转化率的PVAc分级级份的粘度与分子量。提出了以线型和支化聚合物的K,α计算临界分子量的方法。讨论了表征PVAc长链支化的各种参数与分子量和转化率之间的关系以及不同条件下迭代法计算的支化频率λ的差异。实验结果表明,特性粘数和数均分子量乘积所表示的流体力学体积更适合GPC的普适标定概念。     

Random cross-linked poly(styrene-co-maleic anhydride): Characterization of cross-linking intermediates by size exclusion chromatography

The cross-linking reaction of poly(styrene-co-maleic anhydride) (SMA) with ethylene glycol (EG) was monitored using size exclusion chromatography. On-line viscosity and static light scattering detection provided [η] and R_g for structural analysis of the cross-linking intermediates. With increasing reaction time a decrease of the expansion exponent α of the Kuhn-Mark-Houwink-Sakurada relationship was observed. A change from coiled structures to spherical molecules during the cross-linking reaction was confirmed by analyzing the fractal dimensions of the molecules after different reaction times. The calculation of the branching parameters g and g′ revealed the formation of contracted branched molecules. The connection of SMA chains by EG leads to a contraction of the polymers with increasing molecular weight.