p-Toluenesulfonic acid (TsOH) and several alkyl p-toluenesulfonates, that is, methyl p-toluenesulfonate (TsOMe), cyclohexyl p-toluenesulfonate (TsOCH), and neopentyl p-toluenesulfonate (TsONP), were evaluated as initiators for the ring-opening polymerization of benzoxazines. TsOH and TsOMe were highly efficient initiators that induced the polymerization at 60 and 80 degrees C, respectively. In contrast, TsOCH and TsONP did not initiate the polymerization below 100 degrees C, while they induced the polymerization at elevated temperatures, 120 and 150 degrees C, respectively. When TsOCH was used as an initiator, the corresponding polymerization rate was comparable to that observed for the polymerization with using TsOH as an initiator. These results suggested that neutral TsOCH and TsONP can be regarded as "thermally latent initiators," which underwent the thermal dissociation at the elevated temperatures to generate the corresponding alkyl cations and/or TsOH as the initiators of the polymerization. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3631-3636, 2011