Trouble-free combination of ω-alkenylmethyldichlorosilane copolymerization-hydrolysis chemistry and metallocene catalyst system for highly effective and efficient direct synthesis of long-chain-branched polypropylene

Abstract

This paper reports a highly effective and efficient synthesis of long-chain-branched polypropylene (LCB-PP) rendered by combination of ω -alkenylmethyldichlorosilane copolymerization-hydrolysis (ACH) chemistry and metallocene catalyst system. The potential side reaction, the dichlorosilane-methylaluminoxane (MAO) double replacement reaction, is revealed to be slow-occurring and largely suppressible by slightly increasing the steric hindrance of the alkyl substituent(s) on the reactants. Thus, with 5-hexenylmethyldichlorosilane and 7-octenylmethyldichlorosilane of some increased alkenyl chain lengths, the main/side reaction competition dynamics in ω -alkenylmethyldichlorosilane/propylene copolymerization with metallocene ( rac -Me 2 Si-[2-Me-4-Ph(Ind)] 2 ZrCl 2 )-modified MAO complex involving the dichlorosilane-MAO double replacement reaction could shift disproportionally to the main copolymerization to the extent that the effect of the side reaction is not detectable. The synthesized LCB-PPs are characterized by narrow molecular weight distribution, with the LCB structure being H-shape and the interlinkage well defined as 1,2-dihydroxylsiloxane. The successful combination of ACH chemistry and metallocene catalyst system based on conventional metallocene and MAO assures a facile, well-defined, and, most importantly, highly effective and efficient synthesis of H-shape LCB-PP, as compared to two existing outstanding chemistries rendering the same type of LCB-PP, including ACH chemistry combined with heterogeneous Ziegler-Natta catalyst system and nonconjugated α,ω -diolefin copolymerization (NDC) chemistry exercised with 1,9-decadiene and metallocene catalyst system. • ω -Alkenylmethyldichlorosilane copolymerization-hydrolysis chemistry is successfully combined with metallocene catalyst system. • The dichlorosilane-MAO double replacement reaction is weak with ω -alkenylmethyldichlorosilanes of increased alkenyl lengths. • The chemistry results in highly effective and efficient synthesis of H-shape LCB-PP.