Radiation effects on poly(lactide-co-glycolide) (PLGA) and poly(L-lactide) (PLLA)

The purpose of this study is to examine the effects of electron beam (e-beam) radiation on the thermal and morphological properties of biodegradable polymers (PLGA and PLLA), and to understand the radiation-induced degradation that these materials experience. PLGA(80:20) and PLLA polymer films were prepared by solvent casting, and were e-beam irradiated at doses of 5, 10, 20, 30 and 50 Mrad. The degradation of the films was studied by measuring the changes in their molecular weights, FTIR spectra thermal and morphological properties. The dominant effect of e-beam irradiation, in the presence of air, on both PLGA and PLLA is believed to be chain scission. The average molecular weight of PLGA decreases rapidly at low radiation dosage and remains relatively unchanged at high radiation dose (above 20 Mrad). Crystallinity increases with radiation dose for the non-irradiated amorphous PLGA. PLLA also undergoes chain scission upon irradiation but to a lesser degree compared to PLGA. The higher crystallinity of PLLA is the key factor in its greater stability to e-beam radiation compared to PLGA. The glass-transition temperatures (T_g) and melting temperatures (T_m) of both PLGA and PLLA decrease with increasing radiation dosage. Chain scission, though responsible for the reduction in the average molecular weight, T_g and T_m of both polymers, encourages crystallization. E-beam radiation enhances polymer degradation of PLGA and PLLA.