Poly(N-isopropylacrylamide)-based ionic hydrogels were synthesized by free-radical polymerization with N-isopropylacrylamide as a monomer and imidazolium-based dicationic ionic liquid as a crosslinker. The dicationic crosslinkers [Cn(Vim)2][Br]2 were obtained by quaternizing 1-vinylimidazole (Vim) with dibromo compounds (Br-CnH2n-Br) with various alkyl chain length n, respectively. The effects of alkyl chain length and the amounts of crosslinker on the structure, swelling properties, interfacial adsorption and release of anionic dyes of the obtained ionic hydrogels were systematically investigated by using scanning electron microscopy, Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy. The obtained ionic hydrogels showed good swelling properties and typical feature of poly(ionic liquid) in aqueous solutions, of which the quaternized imidazolium moieties could interfacially interact with anionic dyes, such as methyl orange, methyl blue, congo red, orange G, thymol blue and bromothymol blue. Different kinetic and adsorption isotherm models were used to describe the interfacial adsorption and release behaviors of anionic dyes, which were strongly dependent on the chemical structures of the dyes.

The title compound (common name eplerenone), C24H30O6, is an aldosterone receptor antagonist. From the isopropyl acetate solution the compound crystallizes in monoclinic space group P 21 with a = 8.811(1) Å, b = 11.250(1) Å, c = 11.079(1) Å, β = 93.822(12)°, Z = 2. The molecule contains three six membered rings, two five membered rings and one three membered ring. Both five membered rings display envelope conformation, whereas three six membered rings show different conformation: chair, half-chair and envelope. In the crystal the eplerenone molecules link to one another via intermolecular weak C–H···O hydrogen bonding to form the smaller cavity of 12.0(1) Å3 between eplerenone molecules, no solvent molecule filled in this cavity.