# UV-Polymerized Vinylimidazol Ionic Liquids for Permselective Membranes
## 1 Introduction  
Pure salts with a melting point below 100 \({}^{\circ}\)C, so-called \"ionic liquids\" (ILs), have remarkable properties such as low vapor pressure and non-flammability [1; 2; 3]. Due to their synthetic origin, a large number of combinations of anions and cations is possible, as well as the implementation of functional groups [4]. Commonly used structures of cations and anions of ILs are imidazolium, pyrrolinium, phosphonium and halogenide ions [5]. Polymerizable groups, such as vinyl functions, enable one to fix the charges of ionic liquids in materials [6]. These might be hydrogels [7; 8; 9; 10], coatings [11; 12], conductive polymers [13; 14; 15] or polymeric films [16; 17], whereby the synthetic route is not restricted to free radical polymerization and can be extended to other polymerization reactions or even the functionalization of uncharged materials [2; 3; 4; 18; 19; 20]. Recently, [PERSON] et al. reported the influences in the synthesis of polyelectrolytes by the choice of reaction type. Different states of the material, thermal properties or conductivity are not only dependent on the choice of monomers or crosslinkers [21] but also on the synthetic strategy [22; 15; 23]. Besides, these IL materials can be used as catalysts themselves, whereas the process benefits from easy substrate removal [24]. In biomedical applications, hydrogels made of ionic liquids showed no leaching of toxic residuals after the polymerization [25] and in contact with animal cells; on the other hand, interesting antibacterial properties were observed [26]. The toxicity, as well environmental behavior, strongly depends on the structure of the cation and anion [27]. The IL1-ethyl-3-methyl-1H-imidazol-3-ium-acetate has been thoroughly tested and registered within REACH (_Registration, Evaluation, Authorization and Restriction of Chemicals_), and, therefore, a number of tox tests have been made [28]. Polymerized ionic liquids (PILs) are gaining more and more interest in membrane science as they combine the advantages of ILs with those of polymers [15; 29]. Charged membranes potentially increase the fouling resistance and permeability of aqueous solutions [30]. [PERSON] et al. reported a positive effect on antimicrobial activities of ILs but were not able to transfer these properties into the corresponding PIL membranes [31]. In contrast, [PERSON] et al. discovered a reduced number of colonies of _Staphylococcus aureus_ and _Pseudomonas aeruginosa_ while using micro- and ultra-filtration membranes consisting of imidazolium monomers [32]. Another factor that significantly influences the properties of PILs is the length of the vinylimidazolium alkyl chain and the halides. In general, thermal stability is decreased by increasing side chains, while, at the same time, the impact on the glass transition temperature \(T_{\text{g}}\) depends on the anion. Herein, the temperature declines with more complex anions from halogenates towards bistriflimides. Thus, thermal-resistant materials as polyelectrolytes for electroactive devices such as fuel cells or electrode coatings are feasible [16]. Vinylpyridinium PILs were used as an adsorbent for chromium compounds in acidic aqueous solutions [33]. [PERSON] et al. reported similar structures that also retained the heavy metal ions Cd\({}^{\text{II}}\), Zn\({}^{\text{II}}\) and Cu\({}^{\text{II}}\) especially at higher temperatures. The porous material could be regenerated without any losses in adsorption capacity. Regeneration steps were performed with aqueous desorbing solutions containing ethylenediaminetetraacetic, nitric or hydrochloric acid [34]. UV-induced polymerizations represent techniques to fabricate PIL membranes under mild conditions. Due to the high number of charges, these layers were tested as anion exchange membranes in fuel cells [35; 36; 37; 38]. Simultaneously, possible antimicrobial and antibacterial properties are of interest for wastewater treatment or wound-healing [39; 31; 32; 31].