LIVING CARBOCATIONIC POLYMERIZATION OF ISOBUTYLENE USING BLOCKED DICUMYL CHLORIDE OR TRICUMYL CHLORIDE TICL4 PYRIDINE INITIATING SYSTEM

Living polymerization of isobutylene was achieved using an initiation system based on either 1,3-di(1-chloro-1-methylethyl)-5-tert-butylbenzene (tert-butyl-dicumyl chloride) or 1,3,5-tris(1-chloro-1-methylethyl)benzene (tricumyl chloride) in conjunction with TiCl4 and pyridine in hexanes/methyl chloride (60/40, v/v) cosolvents. TiCl4/pyridine was found to yield narrow molecular weight distribution (MWD almost-equal-to 1.1) and quantitative initiation efficiency (I(eff) > 90%). The living nature of the polymerization system was demonstrated by the linearity of molecular weight vs conversion plots and first-order kinetic plots up to about 90% monomer conversion. If polymerization was allowed to proceed further, a departure from first-order kinetics and a broadening of the molecular weight distribution was observed to occur. The living polymerization was investigated as a function of temperature, reaction time, and the concentration of TiCl4/pyridine. Polymerization rates were observed to increase with decreasing temperature and/or increasing concentration of TiCl4/pyridine. Number-average molecular weights of the polyisobutylenes ranged from 5,000 to 100,000 under the conditions employed.