ANIONIC RING-OPENING POLYMERIZATION BEHAVIOR OF A 7-MEMBERED CYCLIC CARBONATE 1,3-DIOXEPAN-2-ONE

Anionic ring-opening polymerization of a seven-membered cyclic carbona te, 1,3-dioxepan-2-one (1), was carried out to observe that the higher the polymerization temperature and lower the initial monomer concentr ation were, the lower the yield and molecular weight, and wider the mo lecular weight distribution of the obtained polymers were. The back-bi ting reaction and the formation of cyclic oligomers of 1 were observed during the polymerization of 1. The relative polymerization rate of 1 was about 35 times faster than that of six-membered carbonate, 1,3-di oxan-2-one (3). The Delta Hps of 1 and 3 estimated by MO (PM3) calcula tions were -9.8 and -4.4 kcal/mol, respectively. 1 could easily underg o the ring-opening polymerization based on larger ring strain. (C) 199 7 John Wiley & Sons, Inc.