Calcium methoxide initiated ring-opening polymerization of epsilon-caprolactone and L-lactide

A commercial calcium dimethoxide and an in-situ generated calcium methoxide prepared from bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] an d methanol, were investigated as initiators for the ring-opening polymeriza tion of epsilon -caprolactone and L-lactide. Commercial calcium dimethoxide initiated rapid epsilon -caprolactone polymerization at 120 degreesC in bu lk to give quantitatively a polymer with a polydispersity index around 1.3. Significant racemization was observed for L-lactide polymerization. The In -situ formed calcium methoxide promoted the solution polymerization of both epsilon -caprolactone and L-lactide to high conversion at room temperature over a short time period, yielding the corresponding polyesters with narro w molecular weight distribution. NMR spectra showed that the poly(L-lactide ) isolated had a purely isotactic microstructure. The initiator efficiency could be tuned by varying the molar ratio of methanol and bis(tetrahydrofur an)calcium bis[bis(trimethylsilyl)amide].