Betaine microgel preparation from 2-(methacryloyloxy) ethyl] dimethyl (3-sulfopropyl) ammonium hydroxide and its use as a catalyst system

• Poly betaine microgel via inverse suspension polymerization.
• Well distributed Ni nanoparticles are prepared within microgels of betaine polymers.
• Highly active p(MEDSAH)-Ni composite catalyst for 4-NP reduction.
• Environmental application of zwitterionic microgel as template and catalyst.

We demonstrate the synthesis of poly(sulfobetain methacrylate) (p(SBMA)) hydrogels of micro dimensions by inverse suspension polymerization of a zwitterionic monomer 2-(methacryloyloxy) ethyl] dimethyl (3-sulfopropyl) ammonium hydroxide (SBMA). The prepared microgels were used as microreactors for the synthesis of nickel (Ni) nanoparticles by in situ reduction of Ni (II) loaded into microgels from an aqueous medium. The prepared microgels and microgel metal nanoparticle composites were characterized by Fourier Transformation Infrared (FT-IR) Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Thermal properties of the microgels were studied by thermal gravimetric analysis (TGA). The amount of Ni nanoparticles generated within the microgels was determined by Atomic Absorption Spectroscopy (AAS) after dissolving the Ni nanoparticles to form Ni (II) ions by treating with concentrated hydrochloric acid (5 M HCl). The prepared composites were used as catalysts for the reduction of nitro aromatic compounds such as 4-nitrophenol (4-NP), 2-nitrophenol (2-NP) and 4-nitroaniline (4-NA) and excellent catalytic performances were observed. The effects of temperature and amount of catalyst were also evaluated. A mild activation energy in comparison to the literature was calculated as 35.64 kJ/mol, and very high kapp value of 0.42 min−1 as a function of temperature was estimated for the reduction of 4-NP catalyzed by p(SBMA)-Ni composite catalyst system.

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