Thermal transformations of acrylonitrile-acrylic acid copolymers : role of carboxy groups

Thermal transformations occurring in polyacrylonitrile and copolymers containing acrylic acid were compared using IR spectroscopy. The presence of carboxy groups induces the hydrolysis of nitrile groups, which occurs concurrently with cyclization, so that the rate of cyclization in the copolymers is smaller than in the homopolymer. Above the glass transition temperature, the carboxy groups associate in clusters, where interactions between the groups become stronger with an increase in temperature.