Poly(lactide-co-glycolide) solution behavior in supercritical CO2, CHF3, and CHClF2

✍ Scribed by S. E. Conway; H.-S. Byun; M. A. McHugh; J. D. Wang; F. S. Mandel

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 159 KB
• Volume: 80
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1199

✦ Synopsis

Abstract

Cloud point and solution density data between 20 and 100°C and pressures to 3000 bar are presented for poly(lactide) (PLA) and poly(lactide‐co‐glycolide) (PLGA~x~, where the molar concentration of glycolide in the backbone x ranges from 0 to 50 mol %) in supercritical CO~2~, CHClF~2~, and CHF~3~. PLA dissolves in CO~2~ at pressures near 1400 bar, in CHF~3~ at pressures of 500 to 750 bar, and in CHClF~2~ at pressures of 20–100 bar. As glycolide (GA) is added to the backbone of PLGA, the cloud point pressure increases by 50 bar/(mol GA) in CO~2~, 25 bar/(mol GA) in CHF~3~, and by only 2.5 bar/(mol GA) in CHClF~2~. PLGA~50~ does not dissolve in CO~2~ to pressures of 3000 bar whereas it is readily soluble in CHClF~2~ at pressures as low as 100 bar at 50°C. In comparison, the increases in cloud point pressure with increasing weight average molecular weight (M~w~) are only approximately 2.3 bar/(1000 M~w~) for PLGA copolymers in CO~2~. The solution densities with all three SCF solvents range from 1.1 to 1.5 g/cm^3^ and they vary only by a small amount over the 80°C range used to obtain cloud point data. More than likely, the ability of the acidic hydrogen in CHF~3~ and CHClF~2~ to complex with the ester linkage in PLGA makes these better solvents than CO~2~ especially since any change in favorable energetic interactions is magnified due to the liquid‐like densities exhibited by these SCF solvents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1155–1161, 2001