Sorption-induced release of antimicrobial isopropanol in EVOH copolymers as determined by ATR-FTIR spectroscopy

This paper deals with the evaluation of the sorption-induced release of an antimicrobial component, i.e., isopropanol, from two ethylene-vinyl alcohol (EVOH) copolymers as measured by ATR-FTIR spectroscopy. Three different swelling agents were considered namely, water, methanol, and ethanol, whose kinetics of diffusion were also evaluated during sorption. From the transport behavior of the latter components, it was found that a pseudo-Fickian diffusion process appeared to take place in all systems. The corresponding simultaneous polymer plasticization was easily followed by evaluation of the sorption-induced thickness expansion and swelling rate. The data indicated that the swelling process appeared to lag the sorption of the penetrant during the first instances of the uptake most probably due to the existence of a Langmuir (antiplasticization) regime previously reported for these polymers. The crossed-diffusion of entrapped antimicrobial isopropanol was related to a typical swelling-induced release process, which was found to be strongly dependent on the nature of the penetrant and on the composition of the polymer matrix. The results demonstrated both the usefulness of the ATR-FTIR technique to uniquely characterize the complex phenomena that take place during sorption-induced release and the suitability of EVOH copolymers for controlled release in antimicrobial applications. (c) 2006 Wiley Periodicals, Inc.