Thermo-sensitive ionic hydrogels synthesis via post quaternization cross-linking: A highly efficient reusable catalytic thermo-responsive nanoreactors

Radical polymerization reactions were employed to synthesize thermo-responsive poly(N-isopropylacrylamide-co-1-vinylimidazole), p (NIPAM-co-VIm), hydrogels at room temperature. A postquaternized cross-linking strategy was reported to fabricate thermo-sensitive quaternized-p (NIPAM-co-VIm) ionic hydrogels, Q-p (NIPAm-co-VIm). Combination of methods (high-resolution X-ray photoelectron spectroscopy, dynamic light scattering, and atomic absorption spectroscopy) was employed to characterize the composite material. Following the concept of a green chemistry, the oxidation of alcohols/olefins was carried out in aqueous solution by using nanocomposites, p (NIPAM-co-VIm) and Q-p (NIPAM-co-VIm). It was found that the catalytic activity of the metal nanocomposite can be modulated by the lower critical solution temperature (LCST) of particles. The catalyst showed improved catalytic activity above LCST. Quaternized composites showed higher catalytic activity than unquaternized counterparts, due to their high hydrophobicity, effective interactions between substrates and catalyst, and high flexibility. In addition, we demonstrated that the catalytic activity of the nanocomposites can be tuned by the volume phase transition within the hydrogel by using the catalytic reduction of 4-nitrophenol/nitrobenzene, NP/NB, as the hydrophilic/hydrophobic substrates model. For 4-NP, with an increase in temperature from 25 degrees C to 35 degrees C (

Automated summary

Radical polymerization was used to synthesize thermo-responsive poly(N-isopropylacrylamide-co-1-vinylimidazole) hydrogels, and a postquaternized cross-linking strategy was employed to fabricate thermo-sensitive quaternized-p(NIPAM-co-VIm) ionic hydrogels. The composite material was characterized using high-resolution X-ray photoelectron spectroscopy, dynamic light scattering, and atomic absorption spectroscopy. The catalytic activity of the metal nanocomposites was modulated by the lower critical solution temperature of particles, and the quaternized composites showed higher catalytic activity due to their hydrophobicity, effective interactions with substrates and catalyst, and flexibility. Additionally, the catalytic activity of the nanocomposites was tuned by the volume phase transition within the hydrogel.