Enzyme-catalyzed ring-opening copolymerization of 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC) with trimethylene carbonate (TMC): Synthesis and characterization

Enzymatic ring-opening copolymerization of 5-methyl-5-benzyloxycarbonyl-1,3 -dioxan-2-one (MBC) with trimethylene carbonate (TMC) was investigated. A r oute to aliphatic polycarbonates decorated with pendent carboxylic acid gro ups is demonstrated. Lipase from Pseudomonas fluorescens (AK) was selected to perform the copolymerization at various monomers feed ratios. Copolymers with different composition were prepared by varying the monomer feed ratio from 10% to 80% MBC. H-1, C-13 and H-1-C-13 HETCOR NMR spectra were used t o analyze the microstructure of the copolymers. The]H NMR spectra indicated lower incorporation of TMC in the copolymer than was expected from the mon omer feed ratio. Analysis of the C-13 spectra did not indicate an ordered s tructure but instead suggested the formation of random polymers. This was f urther confirmed by the thermal data obtained for representative samples. T he thermal properties at different feed ratios of poly[MBC-co-TMC] copolyme rs were investigated by differential scanning calorimetry (DSC). No melting temperature (T-m) for either homopolymers or copolymers was observed. A pl ot of 1/T-g(K) vs the weight composition of MBC in the copolymers was const ructed and was consistent with copolymers that tend toward random distribut ion; this was confirmed from the NMR data.