Dimethylaluminum Chloride Catalyzed Living Isobutylene Polymerization

Abstract

The first examples of dimethylaluminum chloride catalyzed living isobutylene polymerizations are presented. The polymerizations are carried out with conventional tertiary alkyl chloride initiators and 60/40 v/v nonpolar/polar solvent mixtures, the most common solvent systems used for isobutylene triblock synthesis. Additives like proton traps and electron donors are not required. The “living” nature of these polymerizations is demonstrated at −75 to −80 °C in both 60/40 v/v hexane/methylene chloride and hexane/methyl chloride solvent systems using first-order rate plots, trends in Mn and Mw/Mn versus conversion, and delayed incremental-monomer-addition experiments. Polyisobutylenes are prepared with Mn = 150 kDa and Mw/Mn = 1.2. Since initiation from adventitious moisture is of minor concern in this system, experiments were also run in the presence of dimethyl phthalate. “Livingness” was preserved though polymerization rates are slower with dimethyl phthalate than in its absence.