Copolyesters of 1,1'-bis(3-methyl-5-chloro4-hydroxy phenyl) cyclohexane (0.0025 mol), ethylene glycol/propylene glycol/1, 4-butanediol/1,6-hexanediol (0.0025 mol) and terephthaloyl chloride (0.005 mol) have been synthesized by interfacial polycondensation technique by using water-chloroform (4:1 v/v) as an interphase, sodium hydroxide (0.125 mol) as an acid acceptor and cetyl trimethyl ammonium bromide (50 mg) as an emulsifier. The reaction time and temperature were 3 h and 0 degrees C, respectively. The yield of copolymers was 85-87%. Copolyesters are soluble in common solvents and possess moderate molecular weights. The structures of copolyesters are supported by FT-IR and (HNMR)-H-1 spectral data. Copolyesters are characterized for their viscosity in chloroform and 1,2-dichloroetbane at 30, 35 and 40 degrees C, densities by floatation method (1.139-1.2775 g cm(-3)). It is observed that both [eta] and density of copolyesters decreased with increase in alkyl chain length. Copolyesters possess excellent hydrolytic stability against water and 10% each of acids, alkalis and salt at room temperature. The observed wt. % change is +/-3.15% in the selected environments. A 30 mu m thick C1MPT film has 17.8 MPa tensile strength, 50.1 kV mm(-1) electric strength and 2.2 x 10(12) ohm cm volume resistivity. Copolyesters possess high Tg (148-172 degrees C) and are thermally stable up to about 411-426 degrees C and followed single step degradation kinetics involving 70-75% weight loss with 20-24% residual weight above 650 degrees C. Copolyesters followed 1.19-1.94 order degradation kinetics. Activation energy and frequency factors are increased with alkyl chain length.