CATIONIC RING-OPENING POLYMERIZATION BEHAVIOR OF AN ALIPHATIC 7-MEMBERED CYCLIC CARBONATE, 1,3-DIOXEPAN-2-ONE

Synthesis and cationic ring-opening polymerization of a seven-membered cyclic carbonate, 1,3-dioxepan-2-one (1), were examined. The cationic ring-opening polymerization of 1 proceeded without decarboxylation at 20 degrees C to give the corresponding polycarbonate, differently fro m a six-membered cyclic carbonate (2), for which polymerization is gen erally accompanied by partial elimination of carbon dioxide. The obser ved polymerization rate of 1 in nitrobenzene was about 1.3 times faste r than that in dichloromethane. The observed pseudo first-order polyme rization rate constants of 1 and 2 at 20 degrees C were determined to be 4.15 x 10(-4) and 4.16 x 10(-6) s(-1), respectively. The observed p olymerization rate of 1 was 100 times larger than that of 2. The activ ation energies in the polymerization of 1 and 2 were estimated to be 6 .27 and 8.52 kcal/mol, respectively.