单茂钪催化合成高顺式异戊二烯/苯乙烯共聚物的研究

Highly Cis-1,4-selective Copolymerization of Isoprene with Styrene Catalyzed by Half-sandwich Scandium Complexes

合成了5种单茂双烷基稀土配合物Cp＇Ln（CH2C6H4NMe2-o）2（1：Cp＇=C5Me4Si Me3,Ln=Sc;2：Cp＇=C9H7,Ln=Sc;3：Cp＇=C5H5,Ln=Sc;4：Cp＇=C5H5,Ln=Lu;5：Cp＇=C5H5,Ln=Y）在助剂[Ph3C]-[B（C6F5）4]的活化下,考察了稀土金属和配体结构对异戊二烯和苯乙烯的均聚合活性和立体选择性的影响规律.结果表明小空间位阻的单茂钪（C5H5）Sc（CH2C6H4NMe2-o）2（3）催化异戊二烯聚合时,聚合活性和顺式立体选择性较优;催化苯乙烯聚合时获得无规聚苯乙烯.因此选用单茂钪催化剂3/[Ph3C][B（C6F5）4],考察了其催化异戊二烯/苯乙烯共聚合的性能,高活性地获得了组成和分子量可控、分子量窄分布的异戊二烯/苯乙烯多嵌段共聚物.通过1H-NMR,13C-NMR,GPC以及DSC对共聚物进行分析表征,结果表明,通过调控苯乙烯与异戊二烯的加料比例,共聚物中苯乙烯摩尔含量可以在1%~75%间调控,聚苯乙烯嵌段为无规聚苯乙烯;共聚物中聚异戊二烯顺-1,4选择性均大于91%;通过调控单体与催化剂的比例,共聚物分子量（Mn）可以在3.5×104~8.3×104间调控,分子量分布保持窄分布（Mw/Mn=1.71~1.94）.

Five half-sandwich rare earth catalysts Cp＇Ln（CH2C6H4NMe2-o）2（I：Cp＇ = CsMe4SiMe3 ,Ln =Sc; 2：Cp＇= CgH7,Ln = Sc;3：Cp＇ = CsHs,Ln = Sc; 4：Cp＇ = CsHs,Ln = Lu; 6：Cp＇ = CsHs,Ln = Y） were synthesized for homo （co） polymerization of isoprene and styrene activated with [ Ph3C ] [ B （ C6F5 ）4 ] in toluene. The isoprene and styrene polymerization activity, stereoselectivity, molecular weight and molecular weight distribution were studied with these catalysts. The C5H5-ligated scandium complex 3 displayed high activity for the and cis-1,4-selectivity toward isoprene homo styrene homopolymerization simultaneously polymerization, and moderate activity and atactic selectivity By use of this scandium catalyst, the copolymerization of styrene with isoprene was achieved to afford a family of copolymers with high cis-1,4-isoprene content, controlled molecular weight （Mn = 3.5 × 10^4 - 8.3 ×10^4 ） and narrow molecular weight distribution （Mw/Mo = 1.71 -1.94）. The copolymerization activity reach up to 10^5 g of polymer （mol of Sc） -1 h-1. The styrene/ isoprene copolymers were multi-block copolymers with atactic polystyrene blocks, high cis-1,4-isoprene units （ 〉 91%）. The copolymer composition and molecular weight could be easily controlled by changing the feeding ratio of styrene, isoprene and catalyst.