Formation of SBS thermoplastic block copolymer using hexamethyleneimine alkenyl lithium (N‐Li) initiator

Abstract

AbstractStyrene and butadiene block copolymers (SBS) end functionalized with amino group at the initiating chain ends were synthesized using hexamethyleneimine alkenyl lithium (N‐Li) as initiator, tetrahydrofuran (THF) as polar modifier, and cyclohexane as solvent. By attaching a few number of butadiene molecules to N‐lithium hexamethyleneimine, a new N‐Li initiator that can effectively initiate the polymerization of SBS was obtained. 1H NMR spectrums of the N‐Li initiator terminated by ethanol, end functionalized polystyrene, and SBS block copolymer proved the structure of N‐Li and its ability to initiate the polymerization of styrene and SBS block copolymer. Kinetics studies suggested that the polymerization rate of styrene in the first block reached the maximum when the ratio of THF/Li was increased to 5, while further increase of the ratio of THF/Li could not improve the polymerization rate. The molecular weight distribution (MWD) of SBS initiated by N‐Li varied with the ratio of THF/Li. The vinyl content of polybutadiene block increased by improving the ratio of THF/Li, while the content of cis‐1,4 and trans‐1,4 structures decreased. The vinyl content of end functionalized SBS was somewhat higher than that of SBS initiated by classical n‐butyllithium when other condition was the same. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 81–88, 2006