Cationic reactions in the melt

Summary

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a Brabender Plastograph at 180°C. The torque was monitored as a function of time and molecular weights of periodically withdrawn samples were determined.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.