Hits:

Indexed by:期刊论文

Date of Publication:2015-08-01

Journal:POLYMER INTERNATIONAL

Included Journals:SCIE、EI、Scopus

Volume:64

Issue:8,SI

Page Number:1023-1029

ISSN No.:0959-8103

Key Words:propylene; isoprene; copolymerization; metallocene catalyst; regio-chemistry

Abstract:Regio-chemistry control in copolymerization of propylene with isoprene is pursued with C-2-symmetric ansa-metallocene catalysts in order to efficiently synthesize isotactic polypropylene bearing pendant vinylidene functionality (iPP-g-VD) using isoprene as a convenient asymmetric diene feedstock. Two paths are taken by employing two well-known but structurally different metallocenes that exhibit discrepant regio-chemistry for -olefin insertion, namely rac-Me2Si(2-Me-4-Ph-Ind)(2)ZrCl2 (1) and rac-CH2(3-t-Bu-Ind)(2)ZrCl2 (2), both of which tend to an improvement of isoprene 4,3- (primary) insertion specificity whilst depressing the regio-reversed 3,4- (secondary) insertion. In the case of using 1-methylaluminoxane (MAO), the strategy is to use increased dosage of H-2 to effectively integrate isoprene 3,4-insertion into iPP main chain without developing -allyl-metal deadlock. In the case of using 2-MAO, however, the sterically highly hindered ligand structure only accommodates primary isoprene 4,3-insertion. Synthesis of iPP-g-VD becomes much more controllable, with up to 1.91 mol% of side-chain vinylidene groups having been realized on iPP, at fairly good catalyst activities and little or no sacrifice of polymer molecular weight. iPP-g-VD is revealed to be fully eligible as an intermediate for accessing polar-functionalized polypropylene, with both hydroboration and subsequent hydroxylated functionalization and poly(methyl methacrylate) grafting proceeding with high yields. (c) 2015 Society of Chemical Industry