A five-membered cyclic dithiocarbonate having phenylcarbamate moiety 1 underwent cationic ring-opening polymerization by using methyl trifluoromethanesulfonate as an initiator in nitrobenzene at 60 degrees C. Both of the corresponding first-order kinetic plot and conversion-molecular weight plot showed linearity to suggest the living fashion of the polymerization, which was then supported by two-stage polymerization experiment. The living fashion as well as the regioselective formation of the repeating unit suggested significant contribution of the neighboring group participation of the carbamate group to form a stabilized cationic propagating end, of which structure was confirmed by performing an equilmolar reaction of 1 and methyl trifluoromethanesulfonate with analyzing the resulting species by NMR spectroscopy. (c) 2007 Wiley Periodicals, Inc.