Polysiloxane-polyester copolymers have been synthesized for the first time by direct polycondensation of a series of diacids (butanedioic, hexanedioic, and octanedioic acid) and alpha,omega-bis(3-hydroxypropyl) polydimethylsiloxanes catalyzed with Novozyme-435 in high yields (>90%) without the cleavage of Si-O bonds. The effects of monomer chain length, reaction temperature, and water removal method on the number-average molecular weight (M-n) of the resulted copolymers were investigated. Thermogravimetric and differential scanning calorimetry analyses indicated that the produced copolymer was more thermally stable than poly(1,8-octyladipate) and the T-g was lowered to -111 degrees C. (c) 2008 Wiley Periodicals, Inc.