Long chain branched isotactic polypropylenes (LCBPP) prepared via the combination of rac-Me2-Si(2-Me-4-Ph-Ind)ZrCl2/MAO catalyst and a p-(3-butenyl)styrene (T-reagent) were characterized to investigate their synthesis, structure, solution properties, and melt properties. The T-reagent, in the presence of hydrogen, simultaneously served as a comonomer and chain transfer agent, resulting in a LCBPP with high molecular weight, desirable branch point density, and relatively well-defined molecular structure. Additionally, the metallocene catalyst remained highly reactive. To understand the structure-property relationships, a series of LCBPPs were prepared with similar weight-average molecular weights of about 250 000 g/mol and different branch densities ranging from 0 (linear iPP) to 3.3 branch points per 10000 carbons. 1H NMR and SEC equipped with triple detectors revealed structural information. Melt properties were examined by small-amplitude dynamic oscillatory shear and extensional flow measurements. LCBPPs of similar molecular weights 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. Strain hardening was observed in extensional flow of LCBPPs.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry