Preparation, characterization and properties of poly(2,2-dimethyl trimethylene carbonate-co-epsilon-caprolactone)-block-poly(ethylene glycol).

Degradable terpolymers were synthesized by bulk copolymerization of 2,2-dimethyl trimethyle necarbonate (DTC), epsilon-caprolactone (CL) and poly(ethylene glycol) (PEG) using stannous octoate as catalyst at 140 degrees C for 36 h. The molar ratio in feed of DTC to CL was fixed at 20:80. The molecular weight and the mol% of PEG were varied in order to obtain copolymers with different properties. The copolymers were characterized by 1H-NMR, 13C-NMR, FT-IR, GPC and DSC. It was found that the hydrophilicity of these materials increased with increasing PEG content in the copolymers, according to the measurements of static contact angles of distilled water on the surface of polymer films. Mechanical tests and hydrolytic degradation assays showed that copolymers of different degradability and mechanical properties could be tailored by adjusting the compositions. For the copolymer T-4 (11.9 mol% of PEG with Mn 2000), the tensile strength and the elastic modulus could reach 6.2 MPa and 25 MPa, respectively. It took only 4 weeks for the copolymer T-4 to degrade to 83% (M(n,t)/M(n,0)) and 10 weeks to 63% in 0.1 M PBS at pH 7.4 and 37 degrees C. There was no obvious acceleration of degradation rate in vivo in comparison with that in vitro. These materials might be useful for nerve regeneration guides and other biomedical applications.