Polymeric epoxides were converted to corresponding five-membered cyclic carbonates in an effective manner. Poly(glycidyl methacrylate) (PGMA) was converted to a poly(2-oxo-1,3-dioxolane-4-yl) methyl methacrylate (PDOMMA) by the polymer reaction with carbon dioxide using tetraoctylammonium chloride (TOAC) as a catalyst. The miscibility of blends of PGMA or PDOMMA with copolymers of MMA and ethyl acrylate (MMA-EA) of two different EA compositions (2 and 5 wt %) was investigated by differential scanning calorimetry (DSC). The films of PGMA or PDOMMA and MMA-EA (2 and 5 wt %) blends were cast from N,N-dimethylformamide solution. An optical clarity test and DSC analysis showed that PDOMMA blends were miscible over the entire composition range, but PGMA was immiscible with the MMA-EA copolymers. It was also found that the miscibility of PDOMMA with 2 wt % MMA-EA copolymer was better than that of DOMMA with 5 wt % MMA-EA copolymer. The different miscibility behaviors were investigated in terms of Fourier transform IR spectra and interaction parameters based on the binary interaction model.