Cyclic carbonate 9-phenyl-2,4,8,10-tetraoxaspiro-[5,5]undcane-3-one is a six-membered carbonate monomer with a rigid side group. Novel biodegradable poly(carbonate-ester), poly(9-phenyl-2,4,8,10-tetraoxaspiro[5,5]undecan-3-one-co-D,L-lactide) P(CC-co-DLLA), was synthesized by ring-opening polymerization in bulk, using stannous octanoate catalyst. Effects of polymerization conditions such as catalyst concentration, reaction time, and reaction temperature on the polymerization were investigated. The structure of the copolymers was characterized by FTIR, H-1 NMR, and C-13 NMR. Their molecular weights and polydispersity index were determined by gel permeation chromatography. The protecting benzyl ketal group was removed subsequently by catalytic hydrogenation to give a poly(carbonate-ester) containing pendant hydroxyl groups. The in vitro degradation of the copolymers was performed at (37 +/- 0.5)degrees C in two media: phosphate buffer solution (pH 7.4) or Tris-HCl buffer solution (pH 8.6) in the presence of proteinase K. The degradation rate can be regulated by adjusting the composition of two monomers. The pendant hydroxyl groups in the copolymers resulted in a prominent enhancement of the degradation rate in PBS. (c) 2006 Wiley Periodicals, Inc.