Thermally on-off switching membranes of poly(N-isopropylacrylamide) immobilized in track-etched polycarbonate films

The objective of this research was to prepare temperature-sensitive composite membranes for controlled drug release. Cross-linked N-isopropylacrylamide (NIPAAm) polymer network were immobilized into microporous track-etched polycarbonate (PC) films. The effective pore sizes were regulated by the swelling or shrinkage of the PNIPAAm at temperatures at the vicinity of its lower-critical solution temperature (LCST). The resulting membranes were characterized in terms of grafting yield, membrane thickness, Fourier transform infrared (FTIR) spectra and scanning electron micrograph (SEM). The NIPAAm-PC composite demonstrated fast and reversible swelling changes in the 30-40 °C temperature range. The on-off water permeability ratio was significantly higher compared with the literature data. The drug permeabilities of 4-acetamidophenol and ranitidine HCl in the resulting membranes were determined at temperatures between 30 and 40 °C. These membranes exhibited on-off ratios of up to 11 and 20 for the model drugs, respectively. These ratios were stable after 1 month of storage.