Ring-opening polymerization of L-lactide and preparation of its microsphere in supercritical fluids.
The ring-opening polymerization of L-lactide initiated by stannous octoate was carried out in supercritical chlorodifluoromethane (scR22) at various reaction conditions (time and temperature) and reactant concentrations (initiator, monomer, and solvent). The monomer conversion increased to ca. 70% on increasing the reaction time to 1 h. The molecular weight of the poly(L-lactide) (PLLA) product also increased to ca. 160,000 g x mol(-1) over the same period. Increasing reaction temperature from 90 to 130 degrees C resulted in increased monomer conversion and PLLA molecular weight. A series of polymerizations conducted at various 1-dodecanol and stannous octoate concentrations suggested that stannous octoate does not act as an initiator by itself, and that the tin-alkoxide formed from 1-dodecanol and stannous octoate serves as the initiating species in scR22. While enhancements of the monomer conversion and PLLA molecular weight were observed with increasing monomer concentration, the chlorodifluoromethane concentration had the opposite on both. After the polymerization, PLLA microspheres were prepared in situ by using a continuous supercritical antisolvent process without residual organic solvent and monomer to yield highly purified microspheres for environmental and biomedical applications.
Biomaterials Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea.
Ji Won
JW
Pack
Soo Hyun
SH
Kim
Soo Young
SY
Park
Youn-Woo
YW
Lee
Young Ha
YH
Kim
D025924:Chromatography, Supercritical Fluid; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D008970:Molecular Weight; D011091:Polyesters / Q000138:chemical synthesis* / Q000737:chemistry; D013696:Temperature
D011091:Polyesters; C033616:poly(lactide)