Effect of initiators on synthesis of poly(L-lactide) by ring opening polymerization

We studied the effect of several aliphatic alcohols, including1-dodecanol, 1-octanol and methanol, as initiators on synthesis of poly(L-lactide) (PLLA) by ring opening polymerization. The reaction starts with L-lactide monomer and uses stannous octoate as catalyst. Fourier transform infrared spectroscopy and X-ray diffraction analysis verified that PLLAs were produced successfully. Weight, number average molecular weight and polydispersity index of PLLAs were measured by gel permeation chromatography. The PLLA initiated by methanol (PLLA-Meth) presented the highest molecular weight and yield percent. From differential scanning calorimetry, PLLA-Meth showed the highest melting temperature at similar to 167 degrees C, crystallization temperature at 110 degrees C and degree of crystallinity 80%. The thermal stability was assessed by thermogravimetric analysis: this confirmed that PLLA-Meth was superior with the highest degradation temperature compared to PLLA initiated by other initiators. We concluded that methanol was the most appropriate initiator for PLLA synthesis by ring opening polymerization.