Alkyl Zinc Chlorides as New Initiators for the Polymerization and Copolymerization of Isobutene

Mixtures of RZnCl and tBuCl (R = Et) initiate the polymerization of isobutene in the temperature range of (- 35) - (+ 35) degrees C. The order of addition of the reagents is important for effective polymerization. Increasing the solubility of the zinc reagent (R = n-octyl) and use of cumyl chloride as co-initiator provides a system that is active from (-90) - (+35) degrees C. The molecular weights show a remarkably small temperature dependence, E-DP = -3.3 KJ.mol(-1), compared to E-DP = -23 kJ.mol(-1) in classical systems (AlCl3, EtAICl(2)). The molecular weights increase with decrease in zinc concentration and are consistently higher for n-octyl zinc chloride, as expected for a bulkier, less coordinating counteranion polymerizations are not retarded by isoprene addition; homopolymers and copolymers show essentially identical conversions and molecular weights.