CpTiCl2(OR)/MAO体系催化苯乙烯间规聚合的研究

茂金属催化剂广泛应用于催化α-烯烃和苯乙烯的定向聚合. 与传统的Ziegler-Natta催化剂相比, 茂金属催化剂催化活性中心单一, 聚合过程立体定向性强, 且往往得到用常规方法所不能得到的新型聚合物［1～5］. Ishihara等［6］首次采用钛金属有机化合物与甲基铝氧烷(MAO)体系催化苯乙烯聚合, 分离得到间规聚苯乙烯, 从此揭开了苯乙烯定向聚合的新篇章, 合成了大量茂金属有机化合物, 用于催化苯乙烯间规聚合, 其中半夹心结构的茂金属化合物CpTiX3［7,8］, IndTiCl3［3,4,9,10］［Cp=(未)取代环戊二烯基, Ind=(未)取代茚基; X=Cl, F, 烷氧基等］具有最好的催化活性及间规定向性. (CpHMe4)TiF3［8］催化活性高达1.01×108 g PS/(mol Ti*h), 间规度≥95%.

Studies on Syndiospecific Polymerization of Styrene Catalyzed by CpTiCl2(OR)/MAO System

Five new alkoxyl substituted half sandwich complexes CpTiCl₂(OR), R=methoxylethyl(1), methoxylpropyl(2), methoxylisopropyl(3), o methoxylphenyl(4), tetrahydrofurfuryl(5), were synthesized, characterized and tested as catalyst precursors for the syndiospecific polymerization of styrene. When activated with methylaluminoxane(MAO), the new precursors 1-5 exhibited high catalytic activity for the syndiospecific polymerization of styrene and were more active than CpTiCl₃. The differentstructures of alkoxyl ligands affected the activity slightly. When the polymerization was carried in bulk, all the five precursors exhibited high catalytic activity even at low ratio of c (Al)/ c (Ti)=300, the s PS% of the polymer produced by alkoxyl substituted complexes was much higher than that of CpTiCl₃. The polymerization temperature of 70 ℃ was more suitable for this kind of complexes. The existence of the additional oxygen atom in the alkoxyl ligands stabilized the active species at the higher temperature.