Modification of quaternary polymethacrylate films using sodium alginate: film characterization and drug permeability.

The aims of this study were to investigate the molecular interaction of quaternary polymethacrylate (QPM) in aqueous-dispersion form with sodium alginate (SA) and to characterize the physicochemical properties, mechanical properties, and drug permeability of the QPM-SA films. The results demonstrated that QPM can interact with SA via electrostatic force, leading to the formation of flocculate particles in the dispersions. Transparent QPM-SA films were prepared using a casting/solvent evaporation method. The positively charged quaternary ammonium groups of QPM can interact with the negatively charged carboxyl groups of SA, which was observed using ATR-FTIR spectroscopy. This interaction caused a change of thermal properties, an increase in film strength, and a decrease in film tackiness. The puncture strength of the wet films in acidic media increased as the amount of SA was increased, but the flexibility of the films decreased. The wet films still presented good strength and flexibility in neutral pH when using 2.5-6.3%w/w SA because of their lower water uptake in such media. The incorporation of SA into QPM films was able to reduce drug permeability but increase drug diffusivity in acidic media. In contrast, the drug diffusivity decreased with the addition of a small amount of SA into the films when using a neutral medium. This phenomenon can be attributed to the effect of pH on the water uptake of the film and the ionization of the SA in the microenvironment of the films. These findings suggest that SA can modify the characteristics of QPM films, and QPM-SA films present a strong potential for application as a film coating material for modified-release tablets.