苯乙烯基封端反应性等规聚丙烯的催化合成及其在构筑新型拓扑结构聚丙烯高分子中的应用

SYNTHESIS OF STYRYL-CAPPED ISOTACTIC POLYPROPYLENES AND THEIR APPLICATION IN SYNTHESIS OF POLYPROPYLENES WITH TOPOLOGICAL STRUCTURE

在具有高度等规定向能力的rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2/MAO催化体系所催化的丙烯聚合反应中,通过控制聚合条件,实现聚合物链选择性地向对双苯乙烯单体的链转移反应,合成出一种新的苯乙烯基封端的反应性等规聚丙烯.以这种苯乙烯基封端反应性聚丙烯为结构单元,构筑了两种拓扑结构(接枝和星型)的聚丙烯共聚物,一是在CpTiCl3/MAO催化下,与苯乙烯小分子进行配位聚合,合成了以间规聚苯乙烯为主链、等规聚丙烯为侧链的接枝共聚物(sPS-g-iPP);二是选择性地在链端苯乙烯基上进行氯化和取代反应,定量地将叠氮基团引入等规聚丙烯链端,再与多炔基偶合剂进行点击反应,合成了星型等规聚丙烯.

This paper demonstrates the successful synthesis of reactive isotacticpolypropylene terminated with styryl groups.The styryl group was introduced into the iPP chain end via chain transfer reaction to 1,4-divinylbenzene or 1,2-bis（4-vinylphenyl）ethane,during metallocene-catalyzed propylene polymerization by rac-Me_2Si[2-Me-4-Ph（Ind）]_2ZrCl_2/MAO complex in the presence of hydrogen.Although hydrogen does not influence the polymer molecular weight,it greatly affects the catalyst activity.The iPP molecular weight is strongly dependent on the concentration of chain transfer agent.The isotacticity（mmmm） of iPP macromonomers is quite high（≥ 70%）.The polymerization mechanism was also studied by using deuterium as labelled molecule of hydrogen in combination with（（）13C-NMR） technique,and it is clear that the existent double enchainment of chain transfer agent is because the styryl-capped polymer chain would spontaneously insert into Zr—H species with the unique 1,2-manner.The reactive iPP obtained was used as building block,and two kinds of topological structural polymers were synthesized.Styryl-capped iPP was copolymerized with styrene using CpTiCl_3/MAO complex to produce sPS-g-iPP copolymer.Crude copolymer was subjected to extraction with chloroform which resulted in pure graft copolymer free of styryl-capped iPP.DSC results show thatT_m,X_c,and T_c of sPS main chains and iPP side chains are all lower than those of the sPS and iPP homopolymers,separately.The appearance of extremely large supercoolings in sPS main chains is attributed to crystallization starting from homogeneous nuclei in isolated microdomains of graft copolymers which are generated by phase segregation.In addition,the terminal styryl groups of iPP were effectively transformed to azido groups through chlorination and substitutional reaction,and azido-capped iPP was obtained.Then,the click reaction between azido-capped iPP and trialkyne-containing couple agent was conducted in the presence of CuBr/PMDETA.1H-NMR results indicated that the click reaction was fast and highly efficient,and star isopolypropylene was synthesized.