Abstract: The molecular weight distribution of cis-1,4 polybutadiene obtained by polymerization with homogeneous Ziegler catalyst (Et2AlCl-CoCl2-4C5H5N) as well as heterogeneous Ziegler catalyst (i-Bu3Al-Til4) has been determined by means of fractional precipitation. The results show that the molecular weight distribution of both types of polybutadiene is not broad. With regard to the homogeneous catalytic system, the molecular weight distribution becomes narrower when the temperature of polymerization is increased, the monomer concentration lowered, the chain transfer agent added and the cobalt concentration decreased or the Al/Co ratio increased. As to the heterogeneous catalytic system, the homogeneity of molecular weight distribution increases with the lowering of the polymerization temperature and the decreasing of the Al/Ti ratio. But the monomer concentration and aging of catalyst give no evident effect. Molecular weight distribution obtained with heterogeneous catalytic system is narrower than that obtained with homogeneous catalytic system. The peak of differential distribution curve of the former lies on higher molecular weight side, while that of the latter on lower molecular weight side. This is probably due to the fact that the chain terminating rate in the heterogeneous catalytic system depends upon chain length, while that in the homogeneous catalytic system is independent.

摘要： 本工作以逐步沉淀法测定了在均相（Et_2AlCl-CoCl_2·4C_5H_5N）及非均相（i-Bu_3Al-TiI_4）Ziegler型催化剂的作用下,丁二烯在各种条件下进行顺式-1,4聚合的分子量分布。结果指出,不论均相或非均相催化聚合得到的分子量分布都比较窄。对于均相体系,升高聚合温度、降低单体浓度、添加链转移剂（如乙硫醚、N-苯基-β-萘胺、庚烷）、减少催化剂钴的浓度和增加Al/Co比,均能使聚合物的分子量分布变窄;而对于非均相体系,则降低聚合温度和减少Al/Ti比均能增加分子量的均一性;单体浓度和催化剂老化对分子量分布无显著影响。 非均相聚合的分子量分布比均相聚合的更窄,前者的微分分布曲线的高峰偏于高分子量部分,而后者的偏于低分子量部分。这可能是由于非均相聚合的链终止速度依赖于链长,而均相聚合的链终止速度与链长无关。