Stimuli-Responsive Polymer Stabilized Iron Oxide Nanoparticle as Green Catalyst for Styrene Oxidation Reaction

It is essential to replace the conventional toluene chlorination process to produce industrially important benzaldehyde with a more ecofriendly process. In that direction, we have developed polymer-conjugated magnetic nanoparticles as "green catalysts". Poly[(N-isopropylacrylamide-b-acrylic acid)] and poly[(N-isopropylacrylamide-r-N-vinylpyrrolidone)-b-(acrylic acid)] coated magnetic nanoparticles showed high catalytic activity in the synthesis of benzaldehyde by styrene oxidation reaction at room temperature in water using hydrogen peroxide as an oxidizer. The presence of hydrophilic polymers on nanoparticle surfaces improved the aqueous dispersibility, enabling quasi-homogeneous catalysis in water at room temperature. The conversion of styrene to benzaldehyde and styrene oxide can be regulated by varying the temperature, owing to the temperature responsiveness of the block copolymers. Parameters like catalyst concentration, temperature, and time were varied to achieve an optimal reaction condition. The catalysts can be quickly recovered using their magnetic property and reused without noticeable loss in catalytic activity. Thus, these two nanoparticle systems showed great potential for green nanocatalysts in industrial use.