用新型稀土催化剂催化苯乙烯与异戊二烯共聚合

研究了以亚磷酸二异辛酯为配体的氯化稀土配合物(简称Nd)与三异丁基铝(简称Al)组成的二元稀土催化体系催化苯乙烯与异戊二烯的共聚行为,考察了Al与Nd的摩尔比、聚合温度、单体配比等对共聚行为及共聚物组成和链结构的影响。结果表明,该催化体系能够实现异戊二烯的均聚,但不能催化苯乙烯均聚,而催化二者共聚的活性取决于单体配比且低于异戊二烯的均聚。所得产物为无规共聚物,其中异戊二烯链节以顺式-1,4-结构为主(95%～96%),含少量3,4-结构,几乎不含反式-1,4-结构;共聚物中的结合苯乙烯量随Al与Nd的摩尔比、聚合温度及单体配比中苯乙烯量的增加而增大。苯乙烯以孤立单元形式嵌入在异戊二烯链节之间,因此所得共聚物为"准"无规共聚物;共聚物的重均分子量最高可达19.3×105,分子量分布随着共聚物中结合苯乙烯量的增加而变宽,甚至出现双峰分布。

Copolymerization of styrene and isoprene by new rare earth catalyst

The copolymerization behavior of styrene and isoprene was studied in the presence of binary rare earth catalyst system consisting of rare earth chloride complex with diisooctyl phosphate as a ligand(NdCl3·2 DOP,simplified as Nd) and triisobutyl aluminium(simplified as Al).The effects of c(Al)/c(Nd),polymerization temperature,monomer feed ratio on copolymerization characteristics and composition and microstructure of the copolymer were investigated.The results showed that the catalyst could initiate isoprene homopolymerization,but could not catalyze styrene homopolymerization,and the activity of styrene and isoprene copolymerization,which was dependent on feed ratio,was lower than that of isoprene homopolymerization.Isoprene chain in copolymer was rich in cis-1,4-unit(95%-96%),poor in 3,4-unit,and almost free of trans-1,4-unit.Styrene content in the copolymer increased with increasing styrene feed ratio,c(Al)/c(Nd) and polymerization temperature,while the styrene incorporated into the isoprene chain in isolated units,demonstrating the obtained copolymer was quasi-random in chain structure.The weight-average molecular weight of the copolymer could reach up to 19.3×105,and the molecular weight distribution broadened with the increase of bound styrene in copolymer,even the bimodal distribution appeared.