The synthesis and the chemical characterization of some novel random copolyethersulphones of the type P(ESES-co-EES) (Polyethersulphone-ethersuphone:Polyetherethersulphone). is reported. The ESES:EES molar ratio was varied front 80:20 to 20:80 and all the copolymers were terminated with reactive amino groups, and then were fully characterized through (H-1 and C-13)-NMR and MALDI-TOF MS analysis to confirm their chemical structures and chemical compositions. End chains were revealed by these techniques. Contrary to chlorine-ended copolymers, oligomers terminated with hydroxyl groups were revealed in the amine-ended copolymers, indicating that transetherification reactions occur during the capping reaction with m-aminophenol. Cycles were also revealed by MALDI-TOF MS. that revealed also some unexpected end chains may be formed for the impurities in the feed. The glass transition temperatures of the copolymers have been determined by differential scanning calorimetry (DSC). (c) 2006 Elsevier Ltd. All rights reserved.