Copoly(ether-sulfone-sulfonates) of 9,9'-bis (4-hydroxy phenyl) anthrone-10 (BAN) 4,4'-dihydroxy diphenyl sulfone and 4,4' disulfonyl chloride diphenyl ether of varying compositions (PSS-I: 75:25:100, PSS-II: 50:50:100, PSS-III: 25:75:100) were synthesized by an interfacial polycondensation technique using H(2)O-CHCl(3) as an interphase, alkali as an acid acceptor, and CTAB as an emulsifier at 0 degrees C for 3h. PSS-I to PSS-III are characterized by IR and NMR spectral data, viscosity, and density (1.4032-1.4410 g cm(-3)) by the floatation method. PSS-I to PSS-III (73-89m thick) possess, respectively, 9.50, 21.6 and 30 MPa tensile strength; 4.40 x 10(15), 4.30 x 10(15) and 5.50 x 10(14) ohm-cm volume resistivity, and 31.5, 28.0 and 20.5 kV/mm electric strength. Copolymers possess excellent solubility, good hydrolytic stability against water, acids, alkalis, and salt. PSS-I to PSS-III are thermally stable up to about 250-300 degrees C in a nitrogen atmosphere, and are involved apparently in a single-step decomposition reaction. Different magnitudes of kinetic parameters suggested different degradation mechanism.