Spectroscopy techniques for analyzing the hydrolysis of PLGA and PLLA.

The in vitro hydrolytic degradation of irradiated biodegradable polymers was studied. Poly(L-lactide), poly(lactide-co-glycolic acid) (PLGA)(80:20), and PLGA(50:50) polymers were first electron beam irradiated at 5 Mrad before hydrolytic degradation. Hydrolysis of these films was characterized through their physical properties--mass loss, average molecular weight, and thermal properties. Changes to the chemical structures of these polyesters were also analyzed using Fourier-transformed infrared (FTIR) and Raman spectroscopy, and the spectra results were correlated to their physical properties. The results showed that an increase in hydroxyl (OH) group, observed from the FTIR spectroscopy, indicates that the polymer is degrading through hydrolysis--first-stage degradation. Subsequently, a decrease in C==O group, observed from Raman spectroscopy, indicates that the polymer is experiencing mass loss--second-stage degradation. Therefore, a good correlation exists in determining the extent of polymer degradation through the use of FTIR and Raman spectroscopy by observing changes to the OH and C==O groups from the spectra of these nondestructive techniques.