Preparation of High Molecular Weight Poly(L-lactide-co-caprolactone)(75/25)

P(LLA-CL)(75/25) (poly(L-lactide-co-caprolactone)(75/25)) was synthesized from high purity L-lactide and e-caprolactone using tin octoate as initiator by ring-opening polymerization, and characterized by infrared spectrum and 1H-NMR (1H proton spectrum of nuclear magnetic resonance) spectrum. The synthesized P(LLA-CL)(75/25) is a random copolymer. The influences of polymerization temperature, polymerization time and dosage of initiator on the weight average molecular weight and the polydispersity index of P(LLA-CL)(75/25) were investigated. The optimum preparation condition of P(LLA-CL)(75/25) was: the polymerization pressure is less than 0.5 Pa, the polymerization temperature is 125 oC, the n(M)/n(I) ratio is 8,000/1, the polymerization time is 36 h. Under the condition, the weight-average molecular weight of prepared P(LLA-CL)(75/25) is 45.3 104, and molecular weight distribution coefficient is 1.24.