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 SO2 when heated above 160 degreesC in the presence of suitable catalysts. Both quinoline and Lewis acids (BF3 or SnCl4) proved to be useful catalysts yielding polyesters which were characterized by IR and H-1 and C-13 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.