Imidazolium-mediated poly(ionic liquid) hydrogels for multifunctional pollutant removal systems

Abstract

Hydrogels, cross-linked polymer networks that swell enormously in water, have remarkably garnered significant attention as promising materials for various applications such as biomedical engineering, soft robotics, and environmental separation processes. In this study, we report the design and synthesis of imidazolium-mediated poly(IL) hydrogels as multifunctional materials for a wide-range of applications, including high pollutant removal efficiency, enhanced dye adsorption, and controlled drug delivery. To achieve our goal, we have strategically developed a photo-polymerizable bisimidazole monomer featuring three units of ethylene glycol (EG) chain as a spacer between two imidazole rings with a terminal vinyl group. The rational design of crosslinked network architectures within the imidazolium poly(IL) matrix has been exclusively targeted, whereby choosing an appropriate cross-linker, such as poly(ethylene glycol) diacrylate (PEGDA), is anticipated to enhance the performance of the resultant hydrogels. Imidazolium crosslinking at three weight percentage levels affected the physical properties and performance of newly developed hydrogel matrices, which were extensively characterized by Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), as well as their swelling and adsorption properties. Interestingly, the newly developed imidazolium-mediated poly(IL)-derived hydrogels exhibited outstanding adsorption and removal efficiency for both anionic dyes and pharmaceutical products from the aqueous medium. Precisely, while mercuric (HgCl₂) adsorption exhibited complete separation with a q_max value of 217.5 mg g⁻¹, methyl orange (MO) showed adsorption with a q_max value of 158.73 mg g⁻¹, revealing the remarkable ability of the newly developed imidazolium-mediated poly(IL) hydrogels to remove pollutants from water. Furthermore, the hydrogel with the optimal composition, [BImEG₃/PEGDA] [30 : 70], exhibited a good adsorption capacity of 127.22 mg g⁻¹ for sodium diclofenac (DCl), presenting an interesting platform for both dye and drug adsorption systems.