The new cyclic carbonate monomer 2,4,8,10-tetraoxaspiro[5,5]undecane-3-one (DOXTC) was prepared in > 80% yield by the reaction of 1,3-dioxane-5,5-dimethanol with ethyl chloroformate in tetrahydrofuran (THF). DOXTC homopolymerization and copolymerizations with trimethylene carbonate (TMC) were carried out using aluminoxanes (methyl and isobutyl) as catalysts. The copolymer yields normally exceeded 90%. Carbon-13 (13C) nuclear magnetic resonance (NMR) at 62.5 MHz resolved copolymer dyad sequences. Comparison of the fraction of dyad sequences determined by 13C-NMR and calculated assuming a Bernoullian distribution showed that propagation statistics were approximately random for copolymerizations carried out at both 90 and 140℃. Studies by differential scanning calorimetry (DSC) showed that the DOXTC homopolymer, as well as the copolymers with high DOXTC content (FDOXTC to FTMC ≥ 7 : 3), were semicrystalline. The DOXTC homopolymer had a peak melting temperature of 202℃, enthalpy of fusion of 75 J/g, and a glass transition temperature of 36℃. For copolymers with FDOXTC to FTMC ≥ 9/1, crystallization exotherms were observed both during the second heating, as well as cooling (10℃/min) DSC scans. The relationship between the copolymer glass transition and composition was in agreement with that predicted by the Fox equation. Comparison of the wide-angle X-ray scattering (WAXS) patterns of the DOXTC homopolymer with FDOXTC to FTMC of 7 : 3 and 9 : 1 showed that the former sample had more pronounced and better resolved crystalline reflections. These results suggest that the DOXTC homopolymer has well-ordered crystalline domains and high sample crystallinity. By increasing the molar content of 1,3-dioxane side groups in DOXTC-TMC copolymers from 0 to 50%, the water uptake by the corresponding films was increased from 5.1 to 19% (w/w).