Cationic reactions in the melt

Abstract

The effect of Lewis acids of different acidities, i.e., AlCl3 and Bu2SnCl2, on polystyrene melt has been investigated using the mixing chamber of a Brabender Plastograph at 180°C. The torque was monitored as a function of time and molecular weights of periodically withdrawn samples were determined. The structure of select samples has-been analyzed by 1H-NMR spectroscopy. A sequence of complex physical and chemical transformations has been identified. The addition of Lewis acids to polystyrene melts causes an immediate drastic decrease in the torque due to rapid partial polymer degradation which is followed by homogenization and a slower degradation phase. There is evidence for the formation and accumulation of unsaturation during degradation. Cationic reactions induced by the Lewis acids readily explain the observed sequence of chemical transformations.