Electron donor-induced improvement of the microstructure of polypropene-block-poly(ethene-co-propene) synthesized by a modified stopped-flow polymerization method and correlation with its crystalline morphology

Abstract

The influence of electron donors on the synthesis of polypropene-block-poly(ethene-co-propene) (PP-b-(PE-co-PP)) using a modified stopped-flow polymerization method was examined in terms of correlation of the microstructure of the polymer with its crystalline morphology. The results of propene homopolymerization and ethene–propene copolymerization indicated that the application of suitable internal and external donors induced an improvement in the stereoregularity of polypropene (PP) without a decrease in the initial activity and a significant change in the monomer composition and monomer sequence distribution of the poly(ethene-co-propene) (PE-co-PP). The TiCl4/ethylbenzoate/MgCl2 – cyclohexylmethyldimethoxysilane catalyst system was found to produce PP-b-(PE-co-PP) having highly isotactic PP segments. The resulting block copolymers were investigated by cross-fractionation chromatography and differential scannning calorimetry, suggesting that the improved stereoregularity of the PP part in the PP-b-(PE-co-PP) had an effect only on the crystallinity and crystallinity distribution but had no influence on the crystallizability and lamellar thickness of the block copolymer.