Cross-link behavior of an amorphous poly (para-arylene sulfide sulfone amide) synthesized via low temperature solution polycondensation was observed for the first time, when the polymer was subject to a series of thermal curing at 260 degrees C in air condition. The formation of cross-link network was demonstrated by the DSC and TGA results that T-g of the polymer enhanced from 259.17 degrees C to 268.89 degrees C, and the 1% weight loss temperature increased remarkably from 243.75 degrees C to 345.87 degrees C. EPR analysis further suggested that two kinds of free radicals, CO center dot and C-center dot, induced by thermal curing were responsible for this cross-link behavior. According to FT-IR spectrum, the origin of these free radicals was confirmed as amide C=O group in the polymer backbone. The cross-linking type was attributed to conventional radical cross-link reaction and the cross-link mechanism was discussed in detail subsequently. (C) 2011 Elsevier Ltd. All rights reserved.