Thermal degradation of polystyrene and other polymers in the form of ultra-thin films

Abstract

Advantage has been taken of the extreme sensitivity of the technique of thermal volatilization analysis (TVA) to extend degradation studies under relatively mild conditions to very small samples, cast in the form of ultra-thin films down to about 100 Å average thickness; behaviour under these conditions has been compared with that of thicker films and powders. The behaviour of polystyrene has been studied in detail; several other polymers have been investigated less thoroughly. It has been found that some polymers, notably polystyrene and polypropylene, exhibit a very marked increase in thermal stability when degraded in the form of extremely thin films. Poly(α-methyl styrene) and poly( tert.-butyl methacrylate), however, show behaviour which is quite independent of film thickness. Other polymers show behaviour which lies between these two extremes. Stabilization effects are interpreted in terms of a reduction in bimolecular processes during degradation, when films approach monomolecular thickness.