A thermoplastic poly(glycerol sebacate) elastomer (TMPGS), prepared by a two-step method for the first time, is characterized in the present work. First, non-crosslinked poly(glycerol sebacate) (PGS) prepolymers at the 1 : 1 molar ratio of glycerol to sebacic acid were synthesized through a condensation reaction. Second, TMPGSs were achieved through prepolymers that continued to react after the addition of more sebacic acid at a total molar ratio of 2 : 2.5 (glycerol/sebacic acid). The swelling experiments demonstrated that its crosslinking density was low and that it was composed of sol and gel. Compared with our previous results, the content of sol decreased but still reached > 60%. Differential scanning calorimetry (DSC) studies demonstrated that TMPGS was crystallizable and had a glass transition temperature below -20 degrees C, but at close to 37 degrees C, its state altered and became almost amorphous. It was explained that both the semi-interpenetrated polymer networks composed of sol and gel and the crystal regions imparted thermoplasticity to the elastomer. Finally, the in vitro degradation tests illuminated the degradation characteristic of TMPGS in 37 degrees C phosphate buffered saline solution (pH = 7.4). (c) 2006 Wiley Periodicals, Inc.