Thermal oxidation of poly(bisphenol A carbonate) investigated by SEC/MALDI

Thermal oxidation products of poly(bisphenol A carbonate) (PC) generated by heating at 300 and 350 °C, respectively, under atmospheric air, were detected by an hyphenated SEC/MALDI technique. The SEC curves of the thermal oxidised samples showed extensive degradation as a function of heating time, up to the formation of very low mass oligomers. Oxidised PC samples were subjected to SEC fractionation by collecting several fractions which were analysed "off-line" by MALDI-TOF. The MALDI spectra of the SEC fractions of the thermal oxidised PC samples showed the presence of polymer chains containing acetophenone, phenyl substituted acetone, phenols, benzyl-alcohol and biphenyl terminal groups. The mechanisms accounting for the formation of thermal oxidation products of PC involve the operation of several simultaneous reactions: (i) hydrolysis of carbonate groups of PC to form free Bisphenol A end groups; (ii) oxidation of the isopropenyl groups of PC; (iii) oxidative coupling of phenols end groups to form biphenyl groups. The presence of biphenyl units among the thermal oxidation products confirmed the occurrence of cross- linking processes, which is responsible for the formation of the insoluble gel fraction.