Yawei Qin

Recent key developments in isotactic polypropylene in-reactor alloy and in-reactor nanocomposite technology

Alloying and nanocompositing are two most effective techniques by which isotactic polypropylene (iPP), one of the most promising polymers of the 21st century, can be endowed with high performance for ever-demanding high-end applications. Thanks to the continuous advancement of catalyst technology, the technological trend for iPP alloy and nanocomposite fabrication has been projected to be in-reactor synthesis, the performance and economic advantages of which are beyond doubt. In this paper, we review two recent key developments in the iPP in-reactor alloy and in-reactor nanocomposite technology in our laboratory that will have profound influence on the continuing development of the prestigious iPP modification art. The first is the simultaneous EPR (ethylene-propylene random copolymer) cross-linking chemistry for controlling its physical growth pattern during in-reactor alloying, which helps to remove the compositional cap on EPR that so far greatly limits the iPP in-reactor alloying technique. The second is the nanofiller support fabrication strategy for simultaneously controlling both the phase morphology of the nanofiller dispersion and the polymer particle granule morphology of synthesized nanocomposites, which resolves the critical scale-up issue surrounding the iPP in-reactor nanocompositing technique. Based on these new developments, new advancements of iPP materials are envisaged.

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 C2-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.