Abstract: L-lactide(L-LA) and ε-caprolactone(ε-CL) were copolymerized in bulk using stannous octoate as a catalyst. By varying the polymerization monomer feed ratios, copolymers with various compositions can be synthesized. The experimental and theoretical block average sequence lengths based on Bernoullian statistics were calculated from the 1H NMR spectra. With increasing amount of caproyl from 0.1 to 0.5, it is found that the experimental average sequence lengths of the lactidyl units (LeLL) decreased from 20.0 to 4.2, and the experimental average sequence lengths of the caproyl units (LeC) increased from 2.4 to 4.2. The thermal properties of the obtained copolymers were investigated by differential scanning calorimetry (DSC). While the amount of caproyl increased from 0.1 to 0.5, the melting point(Tm) decreased from 161.3℃ to 120.5℃; the heat of melting (△Hm) decreased from 31.5J/g to 8.0J/g; and the glass transition temperature decreased from 51.5℃ to -3.2℃.

Key words: L-lactide, ε-caprolactone, copolymer, microstructure, thermal property