Ring-opening polymerization of D,L-lactide initiated by organictin compounds

Using organic tin compounds,such as tetraphenyltin, tributyltin acetate and stannous octoate as initiators,poly(D,L-lactide) was synthesized by ring-opening polymerization of D,L-lactide.The effects of reaction conditions,such as purity of monomer,polymerization temperature,polymerization time,vacuum level and ratio of initiator to monomer on molecular weight of poly(D,L-lactide) were discussed.The poly(D,L-lactide) was also characterized by IR and 1H NMR.The experimental results showed that the excellent technical conditions are as following:five times recrystallization of D,L-lactide,polymerization temperature 140 ℃,polymerization time 24 h,vacuum level 13.3～133.3 Pa,the ratio of catalyst to monomer 0.2‰～0.5‰,so the viscometric average molecular weight of poly(D,L-lactide)are separately 32.46×104,33.43×104 and 41.36×104.