Carbocationic polymerization of isobutylene with alkyl aluminum chloride/methyl acrylate as the initiating system

Abstract

A solution of alkyl aluminum chloride mixed with methyl acrylate (MA) was prepared and used as the initiating system for the polymerization of isobutylene (IB) carried out in a mixed butane-butene fraction at -50°C. The polymers obtained at different mole ratios A1RmCl3-m_,;, to methyl acrylate ([A1]/[MA]) were characterized by gel permeation chromatography (GPC). The results show that the uncontrolled polymerization process occurring in the absence of MA can be effectively controlled in the presence of small amounts of MA and that it produces polyisobutylene of a narrow molecular weight distribution. The 1H-NMR spectrum of the low-molecular-weight polymer shows that MA acts mainly as an inert electron donor to mediate the polymerization and also partly as an initiator.