High-molecular-weight aliphatic polycarbonates by melt polycondensation of dimethyl carbonate and aliphatic diols: synthesis and characterization

Aliphatic polycarbonates (APCs) synthesized by polycondensation of dialkyl carbonates and aliphatic diols have often been used as precursors for the preparation of novel polyurethanes. However, they could not be applied in plastics directly because of poor mechanical properties caused by low molecular weight. In the work reported in this paper, three kinds of fairly high molecular weight (M(w) >= 166 000g mol(-1)) APCs with narrow dispersity (D <= 1.86) were successfully synthesized via a successive two-step polycondensation of dimethyl carbonate and diols, using a novel TiO(2)/SiO(2)-based catalyst. This process gave a high yield of above 85%. (1)H NMR spectra indicated that there was no detectable decarboxylation happening during polycondensation at high temperature. The effects of molecular weight on the mechanical properties of the APCs are discussed. APCs with M(w) greater than 70 000 g mol(-1) showed useful mechanical properties. Especially, poly(butylene carbonate) and poly(hexamethylene carbonate) exhibited excellent tensile strengths of 34.1 and 40.0 MPa, respectively, when their M(w) was ca 170 000 g mol(-1). All the APCs showed appreciable biodegradability under enzymatic degradation. (C) 2011 Society of Chemical Industry