Cationic Polymerization with Boron Halides. VIII. Synthesis of (CH3)2C = CHCH2-Polyisobutylene-CI Prepolymer and Subsequent Preparation of (CH3)2C = CHCH2-Poly(isobutylene-b-styrene) and (CH3)2C = CHCH2-Poly(isobutylene-b-α-methylstyrene)

Abstract

Abstract Asymmetric telechelic polyisobutylene, α-PIB-ω), carrying the olefinic head group α = (CH3)2 C[dbnd]CHCH2- and tertiary chlorine endgroup ω = -C(CH3)2Cl has been synthesized by the use of the (CH3)2C[dbnd]CHCH2Cl/BCl3 initiating system. Highest yields were obtained by using methylene chloride diluent at about −50°C. The presence and position of the olefinic head-group was proven by epoxidation/titration and epoxidation/cleavage. The presence and position of a tertiary chlorine endgroup was proven by initiating block polymerization of a second monomer, such as styrene or α-methylstyrene, by using the asymmetric telechelic polyisobutylene prepolymer in conjunction with Et2AlCl coinitiator. According to I/DP versus 1/[M] plots obtained in model block copolymerization experiments, with the use of the tert-BuCl/Et2AlCl initiating system at −30°C, significant chain transfer to monomer occurs during blocking of styrene; however, monomer transfer is negligible during blocking of α-methylstyrene. Thus, under suitable conditions head-functionalized block copolymers (CH3)2C[dbnd]CHCH2-PIB-b-PαMeSt virtually free of homopolymer contaminants can be obtained.