Copolymerization of isobutene and α‐methylstyrene as a function of reaction conditions

Abstract

The influence of reaction conditions (solvent, Lewis acid, temperature) on the cationic copolymerization of isobutene and α‐methylstyrene was investigated. The crude product consists of low molecular nonprecipitable oligomers, polyisobutene, and poly(isobutene‐co‐α‐methylstyrene). The amount of poly(α‐methylstyrene) formed under the reaction conditions used was negligible. The degree of charge separation in the propagating cationic intermediate determines the selectivity of the reaction; that is, incorporation of monomer units into the polymer, ratio of different product fractions, and microstructure. Molecular weight distribution, copolymerization parameters, and sequence‐length distribution functions were determined. The softening range of the copolymers depended on their isobutene content but appeared to be constant up to 15% isobutene in copolymers. The degradation temperature of the copolymers was between 340 and 390°C.