Synthesis of butadiene/isoprene-styrene di-block copolymer with high cis-1,4 unit content based on a neodymium phosphate ester.

Abstract

A novel two-step synthesis strategy based on a liquid neodymium phosphate ester (Nd(P507)3) catalyst was used to synthesize diene-styrene di-block copolymers with high cis-1,4 unit content, such as butadiene–styrene (PB-b-PS), isoprene–styrene (PI-b-PS), and so on. The strategy not only makes full use of the high cis-1,4 stereo-selectivity of the rare earth catalyst to conjugated dienes, but also adjusts the electron cloud density of the catalytic active center by introducing triphenyl phosphine (PPh3). Thus, the catalytic activity of the neodymium-based catalyst center toward styrene has been largely improved, and a series of PB/PI-b-PSs with high cis-1,4 unit content (98.3 and 98.1% respectively), narrow molecular weight distribution and controllable block ratio were successfully synthesized. Herein, molecular weight (Mn), molecular weight distribution (Mw/Mn) and microstructure of the block polymers were characterized using SEC-MALLS, FT-IR, 1H NMR, 13C NMR and DSC. The DSC curve of a PB-b-PS with 98.3% cis-1,4 unit and 18.6% polystyrene content shows a Tg of −103.1 °C, which means it has relatively excellent mechanical properties at lower temperature. The results show that these PB/PI-b-PS materials have good application prospects in harsh low temperature environments.