FREQUENCY DEPENDENCE OF THE DIELECTRIC RELAXATION OF 1,2-POLYBUTADIENES

The dielectric loss factor and permittivity of a series of 1, 2-polybutadienes with different contents of 1, 2-units and different contents of syndiotactie 1, 2-units were determined over a frequency range from 30Hz to 100KHz at different temperatures. The WLF equation was evaluated for various samples with T_θat 100KHz as a reference temperature and the master curves of various samples have been constructed, which are in accordance with those calculated by Havriliak-Negami equation. The frequency dependence of the dielectric relaxation of 1, 2-polybutadienes was investigated over a frequency range from 10~0 Hz to 10~(12) ZHz in terms of the experimental data and the master curves.     

可溶性聚苯胺的合成及研究

本文报道了可溶性聚苯胺(PAn)的合成方法。通过对比可溶和不可溶PAn的导电性、电化学行为及IR光谱,说明它们的分子链基本结构相同。并测得了PAn在DMF-d_7中的~13C-NMR 谱。     

1,2-聚丁二烯介电松弛的复平面分析

本文对1,2-聚丁二烯的介电松弛进行了复平面分析.结果表明,在1,2-聚丁二烯的玻璃化转变过程中,ε″(ω)与ε＇(ω)的关系满足Havriliak-Negami方程.由复平面图求出了样品的静态和光频下的介电系数,平均松弛时间和松弛时间分布参数.利用所得数据讨论了1,2-聚丁二烯在玻璃化转变过程中的构象变化、松弛时间分布和平均偶极矩等问题.     

CARBON-13 NMR STUDY OF MOLECULAR MOTION OF 1, 2-POLYBUTADIENES IN SOLUTION Ⅰ. STRUCTURE DEPENDENCE OF MOLECULAR MOTIOM

Proton decoupled, partially relaxed, Fourier-transform 50.3 MHz carbon-13 NMR in naturalabundance was used to determine spin-lattice times (T_1) and nuclear Overhauser enhancement fac-tors (NOE) of individual carbon of a serics of 1,2-polybutadienes with different structures in solutionin CDCl_2 The structure dependence of molecular metion and the internal motion of vinyl group in1,2-polybutadiene have been studied by nT_1 and NOE values. The nT_1 values of the carbons in cis-1,4-units are the highest and those of the carbons in 1.2-units are the lowest in three types of units in1,2-polybutadiene. The nT_1 values of carbons in the same unit become greater when the adjacent1,2-units are replaced by 1,4-units, and nT_1 values of the carbons in all units decrease sharply withthe increase of content of 1,2-units in the polymers. The fact that nT_1 values of --CH=are larger than those of=CH_2 in vinyl group impliesthat there are complex internal motions of vinyl group. It is shown by calculation that the dominantfactor causing the difference in nT_1 of--CH=and=CH_2 in vinyl group is a swing of vinyl group ina plane peopndicular to the chain backbone.     

钼体系催化丁二烯聚合动力学——链转移

本文考察了MoCl_4OC_8H_(17)-(i-Bu)_2Alo催化体系在加氢汽油中催化丁二烯聚合过程中的链转移情况,提出了比较聚合体系中各组分对链转移的贡献大小的方法和计算链转移次数的公式及链转移次数与聚合温度的函数关系式。发现本体系中单体和主催化剂是主要的链转移剂,向烷基铝的链转移占10％,向杂质的链转移仅占6％。在链转移反应中,单体和主催化剂的级数为1,烷基铝的级数为1/2。     

双烯类聚合物的热分析——Ⅱ.不同含1,2-含量无规聚丁二烯热(氧化)的研究

不同1,2-含量无规聚丁二烯的研究表明,与侧链乙烯基相比,主链双键更易于发生热氧化反应,这可能因其含有较多的a-氢。根据热氧化温度和动力学参数活化能E,钴系高1,2-含量间规聚丁二烯比之钼(或锂)系聚丁二烯更为稳定,前者E值高达150kJ/mol以上,后者为100kJ/mol左右。热交联表观活化能分别为181、166kJ/mol。它们热氧化稳定性的差别,是由于通常钴系聚合物为晶态,锂(或钼)系为非晶态。     

蓖麻油基AB交联聚合物的介电性质

在-180℃至140℃范围内,用几个频率测定了蓖麻油基AB交联聚合物的介电松弛谱。对这些聚合物的多重松弛和相行为的研究表明,试样中的两组份在介电松弛谱上显现出相容的或近似互容的特征。试样中的次级松弛归因于聚氨酯组份中链段的局部运动。提出了一个描述界面极化的方法,计算了界面极化松弛活化能,它们同试样中组份间的相容性,界面相互作用大小以及分子链的柔曲性有关。     

1,2-聚丁二烯分子运动的~(13)C-NMR研究——Ⅱ.分子运动的温度依赖性

本文用200MHz脉冲傅利叶变换波谱仪测定了1,2-聚丁二烯样品在不同温度下的~(13)C-T_(19)NOE,线宽和化学位移等~(13)G自旋弛豫参数,研究了1,2-聚丁二烯分子运动的温度依赖性.结果发现,在-10—-30℃之间,样品中各碳核的NOE和谱线宽度随温度变化的曲线斜率增加,表明此时长程链运动冻结;各碳核nT_1随温度的变化均在-45℃左右出现极小值.     

用核磁共振研究浓溶液中高聚物缠结

研究~(13)C-NMR弛豫过程能提供聚合物分子水平上缠结(拓扑和凝聚)的信息.1,2-聚丁二烯在质量分数为25％浓溶液中主链上各基团约有20％产生缠结网络,这个量与样品中1,2-链节含量和溶剂种类无关。而侧链上的端基=CH_2几乎全部是非网络型的,表现为在结点自由地滑动。     

THE MOLECULAR WEIGHT AND ITS DISTRIBUTION OF 1, 2-POLYBUTADIENES PREPARED WITH MOLYBDENUM CATALYST SYSTEMS

The study on the molecular weight and its distribution of 1, 2-polybutadienes prepared with MoCl_4OR-i-Bu_2AlOR' catalyst systems has been carded out by viscosity and GPC methods. 1, 2-Polybutadienes with (?)=1.2-2.0can be obtained with these catalyst systems at 30—70℃. There is a linear relation between the (?) and the polymerization temperature. It was found by extrapolation that these catalyst systems may possibly initiate a living polymerization at the temperature near 18℃. The molecular weight of the polymers can be regulated either by polymerization temperature or by adding polar compounds such as allyl halides.