Multifunctional photo-crosslinked polymeric ionic hydrogel films

A facile approach was developed to prepare crosslinked ionic polymer hydrogel films by photo-crosslinking utilizing p-vinylbenzyl trimethylammonium chloride (VBTMACl) or p-vinylbenzyl trimethylammonium hydroxide (VBTMAOH) as the monomer and poly(ethylene oxide) dimethacrylate (PEODMA, M-n = 750) as the crosslinker. The films with different crosslinking degrees (20%, 40%, 60%, 80%, and 100%) were prepared and characterized by swelling measurements, scanning electron microscopy (SEM), UV-visible spectroscopy, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and small-angle X-ray scattering (SAXS). It was found that the mechanical and thermal properties of the films were largely influenced by the contents of the crosslinker in the films. By ion-exchange of the anions in the films with various other anions, the hydrophobicity/hydrophilicity of the films was changed. In addition, fluorescent films were prepared by treatment with fluorescein, and paramagnetic films with FeCl4- as a counter anion showed catalytic activity for Friedel-Crafts alkylation. The ionic films with quaternary ammonium chloride groups displayed antimicrobial activity against Escherichia coli (E. coli) with almost 100% killing efficiency. Multifunctional films with various tunable properties have significant potential for a wide range of applications.