The effects of methyl acrylate (MA) incorporation (0-15 mol%) on the glass transition, melting behavior, and the peak temperature of the stabilization exotherm in acrylonitrile (AN) based copolymers were studied. A qualitative decrease in crystalline content with increasing MA content was observed using wide angle X-ray scattering (WAXS). The lower crystallinity of the high MA content copolymers could also be noted by the magnitudes of the modulus drop at T-g using dynamic mechanical analysis (DMA) and the step change in heat capacity at T-g using differential scanning calorimetry (DSC). The DSC and differential thermal analysis (DTA) results indicated that the melting temperature of the copolymers decreased with increasing MA content. The magnitude of the crystallization exotherms decreased with successive melting/crystallization cycles. DTA experiments demonstrated that the stabilization reaction, which transforms polyacyrlonitrile into an insoluble, rigid structure, is delayed by the presence of the comonomer. (C) 2003 Published by Elsevier Science Ltd.