One-pot synthesis of Long Chain Branch PP (LCBPP) using Ziegler-Natta catalyst and branching reagents

A new class of long chain branched isotactic polypropylene (LCBPP) polymers with high molecular weights and well-controlled structures are prepared via a combination of roc-Me₂Si(2-Me-4-Ph-lnd)ZrCl₂/MAO catalyst and a T-reagent, such as p-(3-butenyl)styrene. The T-reagent can simultaneously serve two functions (comonomer and chain transfer agent) during metallocene-mediated propylene polymerization in the presence of a small amount of hydrogen. ¹H NMR and SEC equipped with triple detectors revealed most of polymer chain containing LCB structure. LCBPPs displayed a systematic increase in zero-shear viscosity and Arrhenius flow activation energy as branch density increased. LCBPPs with high branch point density displayed thermorheologically complex behavior, and strain hardening was observed in extensional flow.