Telechelic Poly(butylene terephthalate)s by Means of Bismuth Catalysts

Abstract

Dimethyl terephthalate was polycondensed in bulk with a 300 mol % excess of 1,4-butanediol in bulk up to 250 °C. The following catalysts were used Bi2O3, BiCl3, Bi−subsalicylate, bismuth(III) acetate, ZnO, ZnCl2, SnO, SnCl2, Y2O3, YCl3, La2O3, LaCl3, Sb2O3/manganese(II) acetate, and Ti(OBu)4. The highest molecular weights were obtained with Ti(OBu)4. The MALDI−TOF mass spectra revealed that cycles were the main reaction products below 5000 Da. Clean telechelic oligo- and polyesters having two OH end groups were obtained with Bi2O3 and bismuth(III) acetate. With BiCl3, almost clean telechelics having two dimethyl terephthalate end groups were obtained. All other catalysts yield complex reaction mixtures containing cycles and linear chains having CH2OH methyl ester and/or CO2H end groups. At a final reaction temperature of 280 °C, formation of cycles, of CO2H, end groups and of bis(4-oxybutyl) ether units was favored.