The influence of small additives of arenes on low-temperature isobutylene polymerization in an aliphatic solvent

Isobutylene polymerization in hexane at –78 °C initiated by the methanol—aluminum bromide and tert-butyl chloride—aluminum bromide systems in the presence of minor additives (to 10 mmol L^–1) of arenes (benzene, chlorobenzene, toluene, and mesitylene) was studied. The addition of the arenes to a monomer solution has virtually no effect on the polymer yield, whereas the preliminary interaction of a concentrated solution of the Lewis acid with benzene and chlorobenzene sharply increases the monomer conversion and initiation efficiency. The results are interpreteted within a mechanism involving the participation of arene - and -complexes in initiation. The concentration of the complexes is determined by the order of arene addition, and the activity and stability are related to their nature. In these experiments, hexafluorobenzene unexpectedly exhibited a pronounced inhibiting ability.