Magnetic nanoparticles modified by polyamidoamine-immobilized TEMPO for catalytic oxidation of monomethoxy poly (ethylene glycol)

Magnetic nanoparticles (MNPs) modified by polyamidoamine (PAMAM)-immobilized 2,2,6,6-tetramethyl-1-piperidinyl-oxyl (TEMPO) as recoverable catalysts for catalytic oxidation of polyethylene glycol were designed and prepared, which were expected to combine the advantages of easy recovery of MNPs and high activity of PAMAM-immobilized TEMPO. The catalysts of MNPs modified by PAMAM-immobilized TEMPO (MNPs-PAMAM-T) were characterized by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analyzer (TGA), and transmission electron microscopy (TEM). The mean particle size of MNPs was about 10 nm. MNPs-PAMAM-T/NaBr/NaClO was used as catalytic system for catalytic oxidation of monomethoxy poly (ethylene glycol). The catalytic performances were affected by the loading amounts of TEMPO and PAMAM generations. It was shown that the catalyst with TEMPO loading of 5.198 mmol/g using G2.0 PAMAM-modified MNPs as carrier had the best catalytic performance, which could be up to 94% of the free TEMPO level. The efficient recovery of catalyst could be achieved by magnetic separation and the recycling performance was good.