Drug permeation behavior through thermo- and pH-responsive polycarbonate-g-poly(N-isopropylacrylamide-co-acrylic acid) composites

Poly(N-isopropylacrylamide-co-acrylic acid) hydrogel was grafted onto track-etched polycarbonate (PC) films using the free-radical polymerization method to prepare thermo-sensitive micro-porous films. Differential scanning calorimeter analysis was used to determine the lower critical solution temperature for the hydrogels. Thermo-gravimetric analysis was used to determine the thermal stability of the PC–hydrogel composite films. The composite films were characterized using Fourier transform-infrared spectra, scanning electron microscope, and effective pore diameters derived from water permeability data. 4-Acetamidophenol, citric acid, KCl, and methyl orange were used as the model drugs. For neutral drugs, the larger molecules exhibited lower permeability but higher on–off ratio than smaller ones. The strong electrolyte model molecules (KCl) exhibited depressed permeability due to enlarged hydrated ion sizes. The acidic (citric acid) model solution promoted gel shrinkage, resulting in increased drug permeability and on–off ratio.