二茂钛/锡/环氧化合物引发苯乙烯活性自由基聚合的研究

采用单茂钛CpTiCl3和二茂钛金属化合物(n-BuCp)2TiCl2,引发剂4-甲氧苯基缩水甘油基醚(I1),1,4-丁二醇二缩水甘油基醚(I2),4,4′-亚甲基二(N,N-二缩水甘油基苯胺)(I4)和苯基缩水甘油基醚甲醛共聚物(I5)及还原剂Sn组成引发体系,引发苯乙烯活性自由基聚合,合成线型和多臂聚合物.探讨了不同茂钛金属化合物、引发剂和还原剂对苯乙烯聚合的影响;并采用13C-NMR和GPC对聚苯乙烯的结构和性能进行了表征.结果表明所得聚合物是无规聚苯乙烯,聚合物分子量高,分子量分布窄.聚合行为属于活性自由基聚合.

THE INVESTIGATION OF LIVING RADICAL POLYMERIZATION OF STYRENE PROMOTED BY METALLOCENE COMPLEXES/Sn/EPOXIDES

Linear and multi-arm atactic polystyrene with functional groups —OH was synthesized via living free radical polymerization promoted by titanocene complexes in the presence of glycidyl-4-methoxyphenyl ether (I_1), 1,4-butanediol diglycidyl ether (I_2), 4,4′-methylenebis(N,N-diglycidylaniline) (I_4) and poly(phenylglycidyl ether)-co-formaldehyde] (I_5) as initiators, and Sn as reducing agent in this catalyst system. The polymerization mechanism was expatiated. In this article, for the first time, titanocene complexes, for example CpTi(Ⅳ)Cl_3 was treated with Sn to form primary free radical CpTi'(Ⅲ)C1_2 at room temperature, this radical reacted with epoxide(initiator) to give the chain radical which initiated styrene to propagate successfully. The effect of polymerization conditions, such as the structure of the initiator and titanocene complexes, as well as the ratio of initiator to monomers on the performance was investigated. The properties of the obtained polymer were also characterized by GPC. These results showed that the structure of initiator had little influence on the conversion of monomer, the molecular weight and molecular weight distribution of the obtained polymer. Compared with (n-BuCp)_2TiCl_2 and SiMe_2(Ind)_2TiCl_2, half-titanocene, CpTICl_3 was favorable for the polymerization of styrene via radical mechanism. The monomer conversion was more than 80%, the molecular weight of the polymer was higher than 1.0×10~5, and the molecular weight distribution was at the range of 1.18 to 1.42. However, when (n-BuCp)_2TiCl_2 and SiMe_2(Ind)_2TiCl_2 were used as catalysts, the monomer conversion and the molecular weight of the obtained polymer were lower. But the structure of titanocene complex had less impact on the molecular weight distribution (1.26～1.30). The effect of the ratio of monomer to initiator on the polymerization performance was also studied. A linear dependence of M_n of the obtained polymer on the monomer concentration was observed at the ratio of 250/1, 500/1 and 750/1. M_n of the obtained polymer increased with increasing the ratio of monomer to initiator, and the molecular weight distribution of the obtained polymer kept at the range of 1.0 to 1.40. The obtained polymer was also characterized by ~ 13 C-NMR to confirm the atactic structure of the polymer. These results indicated living the free radical mechanism of polymerization.