Synthesis of styryl-capped polypropylene via metallocene-mediated coordination polymerization: Apply to polypropylene macromolecular engineering

In this paper, we review our recent progress in the synthesis and application of styryl-capped polypropylene (PP-t-St), an excellent reactive polyolefin that is both convenient and efficient in synthesis and facile and versatile in application for preparing advanced polypropylene materials via macromolecular engineering. The synthesis of PP-t-St is made possible by a unique chain transfer reaction coordinated by a bis-styrenic molecule, such as 1,4-divinylbenzene (DVB) and 1,2-bis(4-vinylphenyl)ethane (BVPE), and hydrogen in typical C ₂-symmetric metallocene (e.g. rac-Me₂Si(2-Me-4-Ph-Ind)₂ZrCl₂, in association with methylaluminocene, MAO) catalyzed propylene polymerization. The regio-selective 2,1-insertion of the styrenic double bond in DVB or BVPE into the overwhelmingly 1,2-fashioned Zr-PP propagating chain enables substantial dormancy of the catalyst active site, which triggers selective hydrogen chain transfer that, with the formed Zr-H species ultimately saturated by the insertion of propylene monomer, results in an exclusive capping of the afforded PP chains by styryl group at the termination end. With a highly reactive styryl group at chain end, PP-t-St has been used as a facile building block in PP macromolecular engineering together with the employment of state-of-the-art synthetic polymer chemistry to fabricate broad types of new polypropylene architectures.