高精度光电自动计时毛细管粘度计

研制成一种以光导纤维为冷光源的光电自动计时毛细管粘度计以及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。本文介绍了该装置的基本原理、构成、性能指标及主要特点。     

~(238)U自发裂变常数(λ_f)的测定

本文用国际标准年龄样(美国Fish峡谷凝灰岩中的锆石)和天然铀制成的裂变源,分别用裂变径迹年龄对比法和固体径迹探测器法对λ_f值进行了实验测定,对国际标准年龄样,进行了两次反应堆辐照实验,辐照的热中子积分通量分别为7.83×10~(14)n·cm~(-2)和1.38×10~(15)n·cm~(-2),测得的λ_f值为(6.82±0.58)×10~(-17)a~(-1);对8个不同铀含量的裂变源,用固体径迹探测器法测得的λ_f值为(7.06±0.22)×10~(-17)a~(-1),两种方法的平均值为(7.03±0.21)×10~(-17)a~(-1),文中对已发表的用不同方法测得的λ_f值进行了对比,并对影响λ_f测定的因素进行了讨论,建议用(7.03±0.21)×10~(-17)a~(-1)这—λ_f值作为裂变径迹年龄计算中的裂变常数。     

用凝胶渗透色谱测定聚合物中的支化度

本文在Ambler报导的测定聚合物中支化度的工作基础上,提出了支化度的计算方法和电子计算机计算程序,可用ALGOL-60语言在国产DJS-6电子计算机上计算。讨论了支化模型、短链支化和长链支化分布函数等对计算结果的影响,确定了该方法可以相对比较镍系顺式聚丁二烯中的支化度。     

一种手性甲壳型液晶高分子的稀溶液行为及链刚性

用激光光散射和粘度法研究了一系列窄分子量分布的新的手性甲壳型液晶聚合物P1～P6的溶液行为及其链刚性.研究发现四氢呋喃是聚合物P1～P6的良溶剂.在四氢呋喃溶液中,聚合物P1～P6的特性粘数[η]和均方根旋转半径z12对重均分子量Mw的依赖关系分别是[η]=(2.75±0.05)×10-3Mw0.78±0.02和z12=(1.53±0.04)×10-2Mw0.60±0.01.按照YamakawaFujiiYoshizaki蠕虫状圆筒模型的粘度理论和BohdaneckyBushin表达式,求得聚合物的单位围长摩尔质量ML=(29.8±1.0)×102nm,构象保持长度q=(15.4±3.0)nm.q和MHS方程指数α的值说明这类在结构上属于侧链型液晶高分子的聚合物在良溶剂四氢呋喃中呈现比较伸展的刚性链构象,其链刚性与半刚性主链液晶高分子的相似.     

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。     

高性能长链支化聚乙烯制备的研究进展

长链支化聚乙烯（LCB-PE）在聚乙烯链上含有长链的支化结构,因此具有优异的流变性能,从而改善了聚合物的加工性能,这是其它结构聚乙烯所不能比拟的。长链支化聚乙烯的制备方法有辐照法、茂金属共聚法和聚丁二烯加氢法等,本文综述了各种方法的基本原理和优缺点。辐照法制备LCB-PE的优点是比较简便,容易实现工业化生产,但也有制备的LCB-PE结构不明确,高能辐照对设备要求较高的缺点。茂金属共聚法制备的LCB-PE结构较明确,制备过程较易控制,但由于茂金属催化剂的专利问题而不易推广。聚丁二烯加氢法制备的LCB-PE其主链长度、支链长度和支链密度都可控,但过程较复杂,成本高,不易推广。     

凝胶色谱—光散射联机法测定高聚物的长链支化度

运用凝胶渗透色谱-光散射联用技术(GPC-LALLS)测定聚合物的长链支化度的基本原理是:在将聚合物分子按其流体力学体积顺序分离的同时,通过光散射仪逐滴测定溶液中聚合物的分子量。经过对谱图上逐点进行扩展效应的改正,通过普适标定线,求出支化分子与线型分子回转半径的比值,以计算试样的支化度及其分布。具体方法如下:     

长链支化聚乳酸的多重松弛行为

在辐照法制备长链支化聚乳酸(LCB-PLA)的基础上,采用凝胶渗透色谱-多角度激光光散射联用(SEC-MALLS)表征了LCB-PLA的支化结构,利用动态流变学方法考察了PLA的黏弹松弛行为,计算得到了线型及支化PLA在较宽时间范围内完整的加权松弛时间谱.结果表明,由于长支链的引入及支链长度的增加,导致LCB-PLA松弛时间谱加宽,松弛时间增长,并呈现多重松弛行为.提出了一种计算长链支化聚合物支链长度的方法,可以定量表征LCB-PLA的支链长度以及长支链的分子量.     

用正交试验法研制以长碳链季铵阳离子-InBr_4~-缔合物为活性物质的 In(Ⅲ)选择性电极

本文用正交试验法对影响InBr_4~-离子选择性电极的两项主要性能指标的主要因素进行了挑选,确定了一种线性较好、斜率较高的最优因子组合。电极的能斯特响应范围为1×10~(-1)—5×10~(-5)M,斜率56.1±1.1mV/pC,1×10~(-1)—1×10~(-4)M三次级差的平均偏差为2.0±1.0mV/pC。电极的稳定性与选择性较好。     

镉碘络合物的研究 Ⅰ.镉碘络合物的极谱研究

本文用极谱法证明碘离子和镉离子在水溶液中生成配值数自1到6的六种络合物,其各级稳定常数,在以高氯酸钠为维持溶液离子强度的惰性支持电解质时,在25℃时,K_1=40.74±0.4,K_2=(3.72±0.12)×10~2,K_3=(2.95±0.02)×10~4,K_4=(2.37±0.07)×10~5,K_5=(1.04±0.10)×10~5,K_6=(3.70±0.10)×10~4.同时也测定了在18℃和30℃时的各级稳定常数.并计算了在不同配位体浓度时溶液中各种络离子的百分组成,??值和热力学函数(热函,熵和自由能的改变).     

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.     

Dilute solution properties and phase separation of branched low-density polyethylene

Viscosity, light scattering, and precipitation temperature measurements on dilute solutions of high-density and low-density polyethylene fractions have been carried out and a theory by Flory for phase equilibrium of linear polymers has been extended to branched polymer. From the results, it is shown that the entropy parameter ψ, depends on branching; a method for the determination of long-chain branching in polymer fractions is proposed combining precipitation temperature and molecular weight measurements. The method has been applied to the evaluation of long-chain branching in low-density polyethylene.     

Molecular weight and long-chain branching distributions of some polybutadienes and styrene–butadiene rubbers. Determination by GPC and dilute solution viscometry

A method described for the determination of molecular weight and long-chain branching distributions of polymers requires no prior knowledge of the functional relation between branching frequency and molecular weight. It is based on preparative fractionation and viscometric and gel-permeation chromatographic measurements on both fractions and whole polymer. The technique is applied to several polybutadienes and butadiene-styrene copolymers differing widely in method of synthesis and pattern of long-chain branching.     

Long-chain branching in free-radical polymerization due to chain transfer to polymer

The Monte Carlo sampling technique is used to investigate the branched structure formation during free-radical polymerization that involves chain transfer to polymer. This method accounts for the history of the generated branched structure and can provide virtually any structural information, because one can observe each polymer molecule directly. In this paper, we investigate the whole molecular weight distribution (MWD) for both pre- and postgelation periods, the MWDs for polymer molecules containing 0, 1, 2, 3, … branch points, the branching density of polymer molecules as functions of both size and the number of branch points, the spatial distribution of the branched chains at the theta state, etc. Contrary to the term ‘long-chain’ branching, many branch chains are relatively small, and the branched structures formed are significantly different from those usually depicted to introduce ‘branched polymers’ in many introductory textbooks. The radii of gyration at the theta state can be approximated by the Zimm-Stockmayer equation for random branching, in spite of various violations against the assumptions used in deriving the equation © 1995 John Wiley & Sons, Inc.     

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。     

Characterization of low-density polyethylene by gel permeation chromatography—II. Study on the Drott method using fractions

Polyethylenes of different structures were fractionated and the fractions characterized by light scattering, gel permeation chromatography and viscometry. Intrinsic viscosities were measured in solvents of different thermodynamical quality including a θ-solvent (diphenyl at 118° for low-density polyethylene and at 130° for high-density polyethylene and ethylene-butene-1 copolymer). The results were used for examining two aspects of the Drott iterative procedure: (a) the relationship between thermodynamical quality of the solvent and depression in the intrinsic viscosity due to branching; and (b) analytical form of expression relating the so-called g-factor to the number of long-chain branches. The ratio of intrinsic viscosities of branched and linear species at a given weight-average molecular weight has been clearly proved to be solvent independent, and the equation relating the g-factor to the number of branches for polymer monodisperse with respect to molecular weights appears to be a fair representation of long-chain branching in low-density polyethylene. For the polymers examined, the branching frequency λ is not independent of molecular weight.     

Long-chain branching in low-density polyethylene

A method is given for the analysis of long-chain branching in polymers by using combined GPC and intrinsic viscosity measurements. A computer program was written to evaluate branching indices by a tabular, iterative method. The method was applied to the evaluation of long-chain branching in low-density polyethylene.     

辐照高聚物分子量分布的SEC—LALLS表征

本文分析了长链支化存在下,SEC柱扩展效应对测定数据的影响并导出了基本方程组,给出方程组的解法,并通过计算机数值模拟确证此解法的可行性,同时还讨论了扩展效应、改正参数、实验误差对测定结果的影响。在此基础上,建议了以SEC-LALLS联用技术为核心的表征辐照高聚物分子量分布的系统化方法。     

High‐density polyethylene fractionation with supercritical propane

During the development of column extraction techniques, two methods of separation were identified. The first method is based on altering polymer solubility by varying the ratio of solvent in a solvent/nonsolvent mixture at a constant temperature above the polymer melting point (gradient solvent elution fractionation). This method fractionates polymers according to molecular weight. The second method is based on altering polymer solubility by varying solvent temperature (temperature rising elution fractionation—TREF). TREF fractionates semicrystalline polymers with respect to their crystallizability, independently of molecular weight effects. In the present article, supercritical propane will be used to fractionate a high‐density polyethylene sample by molecular weight and short chain branching. The main advantage of supercritical fluid fractionation is that large polymer fractions with narrow molecular weight distributions (isothermal fractionation) or narrow short chain branching distributions (isobaric fractionation) can be obtained without using hazardous organic chlorinated solvents. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 553–560, 1999