LAUSR

Abstract The phase diagram of the binary polymer/drug system poly (lactic acid) (PLA) and N , N -diethyl-3-methylbenzamide (DEET) has been established for the purpose of screening the potential use of biocompatible and biodegradable PLA as drug-delivery reservoir for DEET. Crystallization-induced solid-liquid (S-L) phase separation occurs on sufficiently slow cooling of liquid solutions containing crystallizable PLA at temperatures slightly higher than ambient. Non-isothermal crystallization starts spherulitically at point-like nuclei, followed by dendritic crystal growth due to depletion of crystallizable polymer in the solution in the later stage. Analysis of vacuum-dried crystallized systems reveals formation of intra-spherulitic scaffold-like structures with a pore size smaller than 10 μm. If crystallization is suppressed due to fast cooling or high concentration of stereodefects in racemic random PLA copolymers then liquid-liquid (L-L) phase separation into an almost pure DEET phase and a PLA/DEET solution occurs at temperatures slightly below room temperature. The two liquid phases then vitrify at their respective glass transition temperatures of around −75 °C (DEET) and −15 °C (PLA/DEET).