Phenols/AI(C6F5)3 Initiation Systems for Cationic Polymerizations of Isobutylene

We report herein the cationic polymerization of isobutylene (IB) under mild conditions is realized with a new binary initiation system generated by simply mixing a Lewis super acid Al(C6F5)(3) and a substituted phenol ((PhOH)-Ph-R). Polymers with medium and/or high molecular weights (M-w=4.9x10(4)-27.7x10(4) g.mol(-1)) can be obtained in toluene and temperatures from -20 degrees C to 0 degrees C. NMR spectrum analysis and DFT simulation reveals the in situ generated acidic coordinating complex Al(C6F5)(3)center dot(PhOH)-Ph-R is the initiating active species, which further transformed into the ion-pair [Al(C6F5)(3)(OPh)-Ph-R](-)[P16](+) of the active intermediates upon growing IB monomers where the counter anion [Al(C6F5)(3)(OPh)-O-R](-) coordinates to the macrocation via the phenoxy oxygen. The catalyst performances are the concert effects of the steric bulkiness and electronics of the counter anion on the coordinating strength to the macrocation, which is significant to the stability of the active species.