Physical Properties of PLGA Films During Polymer Degradation

The rates of change of polymer properties (glass transition temperature, weight fraction sorbed water, and polymer molecular weight) were determined in Poly (DL-lactide-co-glycolide) films under accelerated storage conditions. Films were stored at 70 degrees C and 95%, 75%, 60%, 45%, or 28% relative humidity. Weight fraction sorbed water was determined by thermogravimetric analysis, the glass transition temperature (Tg(mix)) of the polymer/water mixture by modulated temperature differential scanning calorimetry, and PLGA number-average molecular weight (M-n) by size exclusion chromatography (SEC). Rates of moisture increase and Tg(mix) decrease were related to the decrease in PLGA M-n through a modification of the Gordon-Taylor equation. Understanding the relative rates of polymer physical and chemical degradation will allow for improved design of PLGA formulations that control rates of drug delivery and preserve drug stability. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2948-2854, 2009