Palladium‐immobilized polymer‐coated magnetic nanoparticles (MNP@polymer‐Pd) were successfully synthesized for use as reusable catalysts for the reduction of 4‐nitrophenol (4NP) in water. The homopolymers and copolymers (e.g. poly(poly(ethylene glycol) methacrylate), PPEGMA; poly(2‐dimethylamino)ethyl methacrylate, PDMAEMA; and poly(2‐diethylamino)ethyl methacrylate, PDEAEMA) were well designed to chemically graft on the surface of the magnetite nanoparticles (MNPs) with the rationalization that PPEGMA improved their water dispersibility and the amino‐containing polymers, e.g. PDMAEMA and PDEAEMA, enhanced the coordinating interaction with Pd and essentially improved their recycling efficiency. The presence of Pd and Fe in the nanocomposites was confirmed via energy‐dispersive X‐ray spectroscopy. The nanocomposites possessed Pd loadings ranging between 0.7006 and 0.8442 mmol g–1. The nanocomposites containing PDMAEMA or PDEAEMA showed higher immobilization efficiency of Pd on their surface than those without these amino‐containing polymers. Interestingly, the nanocomposites having PDEAEMA exhibited an improved catalytic activity for the 4NP reduction compared to those having PDMAEMA. They displayed sustainable reusability for the 4NP reduction after eight cycles without a significant loss in their catalytic performance (99% conversion). © 2022 Society of Industrial Chemistry.

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A thermoresponsive and recyclable nanomaterial was synthesized by surface modification of magnetite nanoparticles (MNPs) with poly(N-isopropylacrylamide-co-diethylaminoethyl methacrylate) (P(NIPAAm-co-DEAEMA)), having PNIPAAm as a thermoresponsive moiety and PDEAEMA for catalyst binding. Palladium (Pd) nanoparticles were incorporated into this material, and the resulting nanocatalyst was efficient in the hydrogenation of olefins and nitro compounds with turnover frequencies (TOFs) up to 750 h −1 . Consistent catalytic activity in 10 consecutive runs was observed when performing the hydrogenation at 45 °C, i.e., above the lower critical solution temperature (LCST) of the copolymer (37 °C), followed by cooling to 15 °C, i.e., below the LCST of the copolymer.

The surface of magnetite nanoparticle (MNP) was modified with poly(acrylic acid)(PAA)-poly(ethylene glycol) methyl methacrylate (PEGMA) (co)polymer to obtain water dispersible MNP with pH sensitive surfaces via atom transfer radical polymerization (ATRP) of tert-butyl acrylate (t-BA), followed by the t-BA group deprotection. Molar compositions of the (co)polymer were systematically varied, namely 100:0, 75:25, 50:50 and 25:75 of P(t-BA)/PEGMA, respectively, such that the grafting density of carboxylate groups on the MNP surface after the deprotection can be fine-tuned. Transmission electron microscopy (TEM) indicated that the MNP were spherical (ca.5-12 nm in diameter) with some nanoclustering observed. The roles of PAA and PEGMA affecting the hydrodynamic size and zeta potential of the nanocomposites observed via photocorrelation spectroscopy (PCS) were discussed. The percentages of the polymeric composition in the nanocomposites in each step of the reaction were determined via thermogravimetric analysis (TGA) and their magnetic properties were studied via vibrating sample magnetometry (VSM). These novel nanocomposites with pH sensitive surface and magnetically guidable properties might be advantageous for further conjugations either by covalent or ionic bonding with bioentities. HIGHLIGHTS Magnetite nanoparticle (MNP) coated poly(acrylic acid)(PAA)-poly(ethylene glycol) methyl methacrylate (PEGMA) (co)polymer were fabricated via ATRP The ratio of t-BA to PEGMA used in the copolymerization was studied The nanocomposites showed pH sensitive surface and magnetically guidable properties GRAPHICAL ABSTRACT