Multifunctional photo-crosslinked polymeric ionic hydrogel films† Hongkun He, ab Brian Adzima, b Mingjiang Zhong, a Saadyah Averick, a Richard Koepsel, c Hironobu Murata, c Alan Russell, c David Luebke, b Atsushi Takahara, d Hunaid Nulwala * ab and Krzysztof Matyjaszewski * ab 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 ¼ 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 FeCl 4  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. Introduction Polymers containing ionic groups or ionic polymers incorporate the properties from both the intrinsic polymers and the extrinsic ionic groups, and have attracted much attention due to their signicant technological applications as well as intrinsic academic interest. Ionic polymers can be classied into two categories: polyelectrolytes that contain anionic or cationic groups and polyzwitterions that contain both anionic and cationic groups. 1 Polymeric ionic liquids (PILs) synthesized from ionic liquid monomers constitute a new class of poly- electrolytes with particular physico-chemical properties. 2 Intensive research into the preparation, structures and prop- erties of ionic polymers has grown remarkably in recent years. 3 In the previous work on the synthesis of ionic polymers, two strategies have been employed: (1) the polymerization directly from ionic monomers, including cationic and anionic mono- mers containing amino, ammonium, sulfonate, or carboxylate groups, 3a and (2) the polymerization from non-ionic monomers followed by post-polymerization modication via sulfonation, 4 quaternization, 5 etc. Both ionic homopolymers and charged- neutral block copolymers have been prepared by step poly- merization, 6 free radical polymerization, 7 and controlled/living radical polymerization (CRP) such as atom transfer radical polymerization (ATRP), 8 and reversible addition–fragmentation chain transfer (RAFT) polymerization. 9 In order to achieve their potential for certain practical applications, it is desirable to process the polymers into lms. Polymers in the form of thin lms oen have different proper- ties from those in the bulk polymers. 10 The techniques for the fabrication of polymeric lms are of two types: the wet pro- cessing, such as solvent casting, dipping, spreading, Langmuir– Blodgett (LB), electro- and photopolymerization; and the dry processing, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), or vapor deposition polymerization methods. 11 The lm preparation procedures can have evident inuence on the properties of the affording lms. 12 Polymeric ionic lm materials have been developed for many applications such as proton exchange membrane fuel cells (PEMFCs), 13 direct methanol fuel cells (DMFCs), 14 dye sensitized solar cells, 15 and ionic polymer–metal composites (IPMCs) for capacitors, 16 a Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fih Avenue, Pittsburgh, Pennsylvania 15213, USA. E-mail: hnulwala@andrew.cmu.edu; km3b@andrew.cmu.edu b National Energy Technology Laboratory, Pittsburgh, Pennsylvania 15236, USA c Institute for Complex Engineered Systems, Carnegie Mellon University, 4400 Fih Avenue, Pittsburgh, Pennsylvania 15213, USA d Institute for Materials Chemistry and Engineering, Kyushu University, CE11 Ito Campus, 744 Motooka Nishi-ku, 819-0395, Japan † Electronic supplementary information (ESI) available: Additional SEM images, photos, ATR-FTIR spectra, 1 H NMR spectra, SAXS data, and uorescence spectra. See DOI: 10.1039/c3py01708g Cite this: Polym. Chem. , 2014, 5, 2824 Received 12th December 2013 Accepted 7th January 2014 DOI: 10.1039/c3py01708g www.rsc.org/polymers 2824 | Polym. Chem. , 2014, 5, 2824–2835 This journal is © The Royal Society of Chemistry 2014 Polymer Chemistry PAPER Published on 08 January 2014. Downloaded by Carnegie Mellon University on 22/04/2015 15:04:02. View Article Online View Journal | View Issue