芳氧基稀土化合物引发开环聚合的活性

综述了近十年来芳氧基稀土化合物在引发内酯、丙交酯和环碳酸酯开环聚合的研究进展,在整理聚合条件、聚合产物收率和分子量、聚合反应动力学和机理的基础上,比较了苯环上不同位置不同取代基的芳氧基配体对开环聚合反应活性的影响,得到以下结论:(1) 三(2,6-二叔丁基-4-甲基苯氧基)稀土化合物Ln(26B4M)3]的活性最高,无取代基芳氧基稀土化合物(La(P)3)没有活性;(2)邻位叔丁基能提高活性,一个叔丁基与两个甲基效果相近;(3)甲基影响作用相对叔丁基较小,甲基越多活性越大.

Ring-Opening Polymerizations Catalyzed by Rare Earth Aryloxides

Recent progress in the last decade on ring-opening polymerizations of lactones, lactides, cyclic carbonates catalyzed by rare earth aryloxides is reviewed. This paper discusses the effect of various substituted aryloxides on polymerization reactivities by summarizing polymerization conditions, monomer conversions, molecular weights of polymers, polymerization dynamics and mechanism. The following conclusions are obtained: (1) The activity of La(26B4M)3 is highest while La(P)3 the lowest. (2) The ortho-butyl group increases the activity of the La(OAr)3. The effect of one t-butyl group is similar to two methyls groups. (3) The effect of methyl groups is less significant than that of butyl groups. Ligands containing more methyl groups give the corresponding catalysts higher activities.