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

Abstract

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.

Smart Poly(N-Isopropylacrylamide)-Based Microgels Supplemented with Nanomaterials for Catalytic Reduction Reactions—A Review

“…The development of HMGs presented by Bera et al [24] is presented in Figure 4. As indicated in Figure 4a, the poly(tert-butyl acrylate) macro-chain transferring agent [p(t-BuA macro-CTA)] was synthesized using S-1-dodecyl-S -(α,α -dimethyl-α -acetic acid) trithiocarbonate (DDMAT) (initiator/chain transferring agent) in the presence of azobis(isobutyronitrile) (AIBN; initiator) and 1,4-dioxane (solvent).…”

“…However, the range of polymerization techniques used for the development of the shell is quite wide in the case of this type of synthetic route. For instance, the polymerization techniques of reversible-addition chain-fragmentation transfer (RAFT) [24] and selective bond Microgels Grown on Pre-Synthesized NMs Core Another route adopted for the synthesis of HMGs is to develop smart microgels on pre-synthesized NMs. This route provides a rigid and compact assembly, as the central component of HMGs is the solid NMs rather than the soft microgel assembly.…”

“…However, the range of polymerization techniques used for the development of the shell is quite wide in the case of this type of synthetic route. For instance, the polymerization techniques of reversible-addition chain-fragmentation transfer (RAFT) [24] and selective bond formation techniques [25] have been used alongside FEPol for the development of HMGs. Li et al [26] synthesized Au NPs using citrate reduction methodology and anchored two successive shells of PNIPAM layers (via FEPol) over these NPs by carrying out a polymerization reaction containing the dispersion of Au NPs in the reaction pot.…”

“…Bera et al [24] developed iron oxide (Fe 3 O 4 ) NPs via a co-precipitation reaction where two soluble salts (including ferric chloride and ferric sulfate) were simultaneously used in the presence of NaOH to precipitate in the form of Fe 3 O 4 NPs. This methodology is crude but effective at synthesizing NPs that are stable at lower temperatures (80 to 150 • C).…”

Ultrasound-Mediated Atom Transfer Radical Polymerization for Polymer-Grafted Magnetic Nanoparticles with Controlled Packing Density

“…Magnetic nanoparticles (MNPs) and their assemblies have attracted increasing attention due to their wide potential applications that range from biomedicine − to information storage − sensors , and catalysts . Nanoparticles with stable room-temperature remanent magnetization, i.e., nanomagnets, have been suggested for applications in nonvolatile magnetic memories, where each nanomagnet acts as a memory bit.…”