Poly(hydroxyisobutyrate) by ring-opening polymerizations of 5,5-dimethyl-1,3,2-dioxithiolan-4-one-2-oxide

alpha-Hydroxyisobutyric acid anhydrosulfate HiBAS (5,5-dimethyl-1,3,2-dioxithiolan-4-one-2-oxide) was polymerized under various reaction conditions and the solid reaction products were characterized by H-1 NMR spectroscopy, MALDI-TOF mass spectrometry (MT m.s.), fast atom bombardment mass spectrometry (FAB m.s.), viscosity, and SEC measurements. Thermal polymerizations at 100 degrees C mainly yielded cyclic oligo polyesters presumably resulting from a zwitterionic polymerization. Cycles were also detected when pyridine was used as catalyst at 20 degrees C. When triethylamine was used as catalyst traces of H2O played the role of initiators. Benzyl alcohol initiated the polymerization of HiBAS at 100 degrees C and yielded a polyester terminated by one benzylester and one OH endgroup. The SEC measurements indicated that all samples possess relatively low molar masses with number-average molecular weights <= 10,000 Da (in contrast to the literature data). (C) 2008 Wiley Periodicals, Inc.