High-molecular-weight copolyesters based on poly(butylene terephthalate) as rigid aromatic segments and poly(l-lactic acid) (PLLA) as degradable aliphatic segments were synthesized via the polycondensation of terephthalic acid, 1,4-butanediol (BDO), 1,4-cyclohexanedimethanol (CHDM), and PLLA oligomer. By tailoring the molar ratio of diols (BDO and CHDM), we investigated in detail the effects of the CHDM rigid hexacyclic ring on the synthesis, mechanical properties, thermal stabilities, and degradation behaviors of the copolyesters. With increasing CHDM content, the initial decomposition temperature increased from 282.5 to 322.2 degrees C, and the tensile strength improved by nearly four times, from 5.4 to 19 MPa. When the molar ratio of BDO/CHDM was 95/5, the weight-average molecular weight of the copolyester was 89,400 g/mol with a polydispersity of 1.96. In addition, hydrolytic degradation results in phosphate buffer solution indicate that the degradation rate of the copolyesters displayed a strong dependency on the temperature and CHDM composition. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2985-2995, 2011