The effect of 1,2-dipiperidinoethane derivatives on the composition and hydride sequence distribution in the LAP of styrene and isoprene

Abstract

Precise control of monomer sequences is of significant importance for the functional modification of polyolefins. For styrene/isoprene (ST/IP) random/alternating copolymers with a constant composition, F_ST = 0.5, variations in the content of isomeric 1,3-diene units in alternating sequences (ST-alt-1,4-IP, ST-alt-3,4-IP and ST-alt-1,2-IP) significantly influence the properties of polyolefins. In this paper, a sterically hindered active center was constructed using 1,2-dipiperidinoethane (DPE)-derived polar additives and n-butyllithium. The regulatory effects of these novel structure regulators on copolymer composition distributions and isomeric unit sequence distributions were systematically characterized by ¹H NMR spectroscopy, and the microstructure information was further verified by FTIR and DSC analyses. GPC analysis confirmed the living and controllable nature of the copolymerization. Finally, the thermal performance differences of random copolymers with various hybrid sequence distributions were systematically investigated by DSC. These research results advance the understanding of sequence regulation polymerization mechanisms and provide a novel strategy for the controlled preparation of liquid rubber.