LIVING CARBOCATIONIC POLYMERIZATION OF P-METHYLSTYRENE AND SEQUENTIALBLOCK COPOLYMERIZATION OF ISOBUTYLENE WITH P-METHYLSTYRENE

A novel scheme was developed for the synthesis of pure polyisobutylene -poly(p-methylstyrene) block copolymers by sequential monomer addition . The synthesis involves the living polymerization of isobutylene by t he TiCl4/methyl chloride:methylcyclohexane or hexanes 40:60 v:v/-80-de grees-C system in the presence of di-tert-butylpyridine. When the poly merization of isobutylene is complete, the living polyisobutylene chai n end is transformed to the corresponding diphenyl alkyl end by cappin g with 1,1-diphenylethylene. Subsequently, titanium(IV) isopropoxide o r titanium(IV) butoxide is added to decrease the Lewis acidity followe d by the addition of p-methylstyrene. The success of the method was de monstrated by p-methylstyrene homopolymerization experiments initiated by 2-chloro-2,4,4-trimethylpentane that resulted in approximately 100 % initiator efficiencies when the TiCl4/titanium(IV) isopropoxide or - butoxide ratio was less than 25/7, as well as by the clean synthesis o f polyisobutylene-poly(p-methylstyrene) diblock copolymers.