Photochromic Behavior of Inorganic Superporous Hydrogels Fabricated from Different Reacting Systems of Polymeric Deep Eutectic Solvents

Abstract

New superporous hydrogels (SPHs) have been fabricated by a one-pot room temperature assembly of poly(acrylic acid) (PAA) and acrylamide (AAm). Tungsten oxide-molybdenum oxide nanocomposites were prepared from different reacting systems of polymeric deep eutectic solvents (PDESs) and incorporated into the polymer network as a chemical crosslinker to form P(AA-AAm)@WO3/MoO3 SPHs. The SPHs formed from N-methyl pyrrolidone (PYR), water (H2O), and dimethylsulfoxide (DMSO)-based PDES systems displayed good mechanical properties and remarkable swelling rates at high pH. The SEM topology of the hydrogels shows a non-uniform pore opening (confirmed by mercury intrusion porosimetry analysis) that could entrap the distributed nanocomposite particles, thereby serving as channels for transporting photogenerated electrons and holes. Under UV-light irradiation, the PYR-, H2O-, and DMSO-based SPHs changed from colorless to blue, blue-black, and faint blue-black colorations after 300 s, 60 s, and 45 min of irradiation respectively. These respective hydrogels faded after 40 min, 25 min, and a few seconds under room temperature conditions. The inherent rich oxygen vacancies in the WO3/MoO3 nanocomposites can boost charge transfer leading to enhanced photoredox performance and fading. Owing to the porosity and good photochromic behavior of the materials, it could open new avenues for next generation adsorption and photochromic materials for many applications.