Phase behavior of the polymer/drug system PLA/DEET. (22nd September 2017)

• Record Type: Journal Article
• Authors: Sungkapreecha, Chanita; Iqbal, Naeem; Gohn, Anne M.; Focke, Walter W.; Androsch, René
• Is Part Of: Polymer. Volume 126(2017)
• Page Start: 116
• Page End: 125
• Publication Date: 2017-09-22
• Subjects: PLA/DEET phase diagram -- Solid-liquid phase separation -- Liquid-liquid phase separation -- Crystallization -- Scaffold structure -- Drug delivery; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2017.08.031
• Languages: English
• ISSNs: 0032-3861

Abstract

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). Graphical abstract: Highlights: The phase diagram of the polymer/drug system PLA/DEET has been established. PLA and DEET are miscible at elevated temperature. S-L and L-L phase separation were studied using crystallizable and amorphous PLA. Crystallization of PLLA in presence of DEET leads to scaffold formation.