The influence of chain rigidity on the thermal properties of some novel random copolyethersulfones

Some random low molar mass (Mnz9000 g mol1) poly(ethersulfoneethersulfone)/poly(ethersulfoneethersulfonebiphenylsulfone)P(ESES)/P(ESESBS) copolymers, with various (25%, 50% and 75%)ESESBS units contents, were synthesized to obtain compounds with higher chain rigidity than PES.The thermal characterization of the prepared copolymers, as well as that of corresponding P(ESES) andP(ESESBS) homopolymers, was performed, and all investigated parameters showed strong dependenceon polymer composition.The glass transition temperature (Tg) was calorimetrically determined by DSC technique, and theobtained values increased linearly as function of ESESBS units percentage, thus indicating an increasingchain rigidity.Degradations were carried out in dynamic heating conditions, from 35 C to 700 C, in both flowingnitrogen and static air atmosphere, and the characteristic parameters of degradation were determined inorder to draw useful information about the overall thermal stability of the studied compounds. Theapparent activation energy of degradation (Ea) was obtained by the Kissinger method, and the valuesfound increased linearly as a function of ESESBS content, while the temperature values at 5% mass loss(T5%) showed an opposite linear trend. The results are discussed and interpreted.