High-pressure stopped-flow polymerization for polypropene-block-poly(ethene-co-propene) having controlled molecular weight: Synthesis and characterization

A high-pressure-type stopped-flow polymerization system was developed for t he production of a real block copolymer, polypropene-block-poly(ethene-co-p ropene), having a variable molecular weight. The preliminary homopolymeriza tion experiments of propene at 1-6 atm for 0.1 s with an MgCl2-supported Zi egler catalyst and TEA indicated that the polymer yield and molecular weigh t of the resulting polypropene were proportional to the monomer concentrati on in the system. This indicates that the catalyst activity is constant and the unfavorable side reactions can be negligible, i.e., independent of the monomer pressure. The higher propene and ethene concentrations, which coul d be regulated by the pressures of the vessels in the apparatus, were found to induce a higher molecular weight of the resulting block copolymer witho ut a significant change in the molecular weight distribution and microstruc ture. The CFC, DSC, and AFM analyses results indicated that the increased m olecular weight had an influence only on the lamellar thickness but had no effect on the crystallinity and its distribution of the block copolymer.