Effects of Anion and Cross-Linker on the Surface Hydrophilicity and Selective Solvent-Induced Swelling of Poly(ionic liquid) Elastomers

Abstract

Poly(ionic liquid)s (PILs) have attracted great attention because they preserve conventional characteristics of polymers while having special features of ionic liquids, such as good ionic conductivity and excellent electrochemical and thermal stability. The solvent absorption behaviors and solvent-induced responsiveness of PIL elastomers, however, have been less investigated. In this work, we prepare two PILs, poly[C3mim-MA][Br] and poly[C3mim-MA]-[TFSI], and examine their surface hydrophilicities and solvent-induced responsiveness. Ionic liquid monomers are synthesized and then polymerized with initiators and cross-linkers via free radical polymerization, forming PIL elastomers. The anions in the monomers can be replaced using an ion exchange process to prepare PIL elastomers with different anions. The surface properties, swelling behaviors, and solvent responsiveness of the PIL elastomer films with different anions and cross-linker ratios are investigated. The surface hydrophilicities of the PIL films are characterized by water contact angle measurements; the poly[C3mim-MA][Br] elastomer films are more hydrophilic than the poly[C3mim-MA][TFSI] elastomer films. Due to the different hydrophilicities, the poly[C3mim-MA][Br] and poly[C3mim-MA][TFSI] elastomer films can be swollen selectively in water and acetone, respectively. For both elastomers, the swelling degrees are higher at lower cross-linking densities, and the volume expansions can be up to 655%. Furthermore, we investigate the solvent-vapor-induced responsiveness of bilayer films of PIL elastomers and polyimide (PI) tapes. The bilayer films can be bent selectively by exposing them to water or acetone vapors, depending on the anions.

Solid-state, liquid-free ion-conducting elastomers: rising-star platforms for flexible intelligent devices

“…In addition to commercial cationic IL monomers, some synthetic IL monomers have also been prepared via the ion exchange reaction. 30,75–78 One impressive case is the synthesis of the polymerizable [2-(methacryloyloxy)ethyl]trimethylammonium bis(trifluoromethanesulfonyl) imide [MATAC][TFSI], followed by one-step polymerization without chemical crosslinking for the construction of a fluorine-rich poly[MATAC][TFSI]-based ionic conductor (Fig. 6a).…”

Terbium based (poly)ionic liquids for anti-counterfeiting and droplet manipulation

“…The magnetism of magnetic ionic liquids and magnetic poly(ionic liquid)s (M(P)ILs) is generated by high-spin transition metals in anionic complexes. 23 M(P)ILs show excellent properties, such as good machinability, 24 a wide electrochemical window, 25 high ion conductivity, 26 durability 27 and thermal stability. 28 Compared with inorganic magnetic materials, M(P)ILs benefit from the characteristics of ionic liquids and organic magnetic components, exhibiting flexible structural design 29 and ease of processing.…”

Developing Stretchable and Photo-Responsive Conductive Films by Incorporation of Spiropyran into Poly(ionic liquid)s

“…14 Recently, we also reported selectively solventresponsive PILs by comparing different anions and crosslinker ratios. 15 Despite these studies, unique stimuli-dependent properties of PILs, especially photo-regulated electrical conductivities, however, have not yet been fully accomplished.…”

“…In another example, Mandal et al studied the ion and thermo-responsive PILs by connecting imidazolium-based PIL to perylene bisimide and fabricating multiresponsive nanoparticles via microwave-assisted polymerization . Recently, we also reported selectively solvent-responsive PILs by comparing different anions and crosslinker ratios . Despite these studies, unique stimuli-dependent properties of PILs, especially photo-regulated electrical conductivities, however, have not yet been fully accomplished.…”