New Polymer Syntheses. 110. Ring-Opening Polycondensation of Two Cyclic Monomers−Polyesters from Ethylene Sulfite and Cyclic Anhydrides

Ethylene sulfite and succinic anhydride undergo a polycondensation reaction evolving SO 2 when heated above 160 °C in the presence of suitable catalysts. Both quinoline and Lewis acids (BF 3 or SnCl 4 ) proved to be useful catalysts yielding polyesters which were characterized by IR and 1 H and 13 C NMR spectroscopy. Analogous polycondensations were conducted with mixtures of ethylene sulfite and glutaric anhydride, 3,3-tetramethylene glutaric anhydride, adipic anhydride, and sebacic anhydride. The resulting polyesters had number average molecular weights ( M n s) in the range of 5000−10 000 Da (based on PS-calibrated SEC), and the MALDI−TOF mass spectra indicated the formation of cyclic oligoesters and polyesters along with linear chains. Polycondensations of ethylene sulfite and succinyl sulfide yielded S-free polyesters, a result important for the mechanistic discussion. No polycondensations were observed for mixtures of ethylene sulfite and dicarboxylic acids, whereas oligoesters containing diethylene glycol units were obtained from acid-catalyzed polycondensations of ethylene glycol and cyclic anhydrides. The unusual thermodynamic aspects of this ring-opening polycondensation concept are also discussed.