Ring-Opening Dispersion Polymerization of _L-Lactide with Polylactide Stabilizer in Supercritical Carbon Dioxide

摘要

Non-fluorous triblock copolymers of poly(L-lactide)-block-hydroxypropyl-tcrminated poly(dimcthyl siloxancs)-block-poly(L-lactidc) (PLLA-HTPDMS-PLLA）with two different molecular weights in the range of 4800 to 6500 Da, were prepared by changing the ratio of HTPDMS to _L-lactidc (L-LA)，and were used as stabilizers for the ring-opening dispersion polymerization (RODP) of L-LA to prepare poly(_L-lactidc) (PLLA) in supercritical carbon dioxide (ScCO_2). The experimental results showed that the prepared non-fluorous triblock copolymers were very effective as new stabilizers for the RODP and fine powders of PLLA were obtained. The structure of the stabilizers and PLLA were characterized by ~1H NMR and FTIR spectroscopy. The morphology of PLLA was investigated by scanning electron microscopy (SEM). The effects of the CO_2-philic/lipophilic segment lengths of the stabilizers on the RODP were explored. The cffccts of the stabilizer concentration on the polymerization yield, molecular weight, and morphology of PLLA were investigated.