Synthesis and properties of α-substituted benzylpyridinium salts as cationic initiators

α-Methylbenzylpyridinium SbF₆ (1a) and α,α-dimethylbenzylpyridinium SbF₆ (1b) were prepared and the effect of α-methyl groups on the active species and the activity of 1a, 1b during the cationic polymerization of glycidyl phenyl ether (GPE) was evaluated. 1b was prepared by the reaction of α,α-dimethylbenzyl alcohol with pyridinium hexafluoroantimonate (2) in several solvents, and the yield depended on the dipole moment of the solvents, although it was poor for the reaction of α,α-dimethylbenzyl chloride with pyridine for the steric hindrance of the α-methyl groups followed by exchange with NaSbF₆. Both 1a and 1b acted as a latent thermal initiator during the cationic polymerization of GPE and 1b showed higher activity during cationic polymerization with the higher steric effect of the α-methyl groups than 1a. The ¹H-NMR analysis of the obtained poly GPE indicated that the active species of 1b changed from the benzyl cation to H⁺, depending on the reaction temperature, although 1a released benzyl cations as active species in the cationic polymerization of GPE. © 1996 John Wiley & Sons, Inc.