Poly[N-isopropylacrylamide-co-3-(trimethoxysilyl)-propylmethacrylate] Coated Aqueous Dispersed Thermosensitive Fe3O4 Nanoparticles

This paper reports a facile synthesis of thermosensitive Fe 3 O 4 nanoparticles coated with poly( N -isopropylacrylamide)-related copolymer in aqueous solution. A functional monomer, namely 3-(trimethoxysilyl)propylmethacrylate (TMSPMA) with methoxysilyl group (-SiOCH 3 ) was copolymerized with N -isopropylacrylamide (NIPAm) to yield a thermo-sensitive copolymer, poly[ N -isopropylacrylamide- co -3-(trimethoxysilyl)propylmethacrylate] [P(NIPAm- co -TMSPMA)]. Such copolymer hence possesses the capability for the silanization of the Fe 3 O 4 nanoparticles. Thermo-sensitive P(NIPAm- co -TMSPMA) capped Fe 3 O 4 nanoparticles were then easily obtained by in situ synthesis of Fe 3 O 4 nanoparticles in the presence of the copolymer in aqueous solution. The Fe 3 O 4 nanoparticles have mean diameters around 12 nm. The P(NIPAm- co -TMSPMA) capped Fe 3 O 4 nanoparticles show thermo-sensitive properties. With thick grafted P(NIPAm- co -TMSPMA) layer, the thermo-sensitive behavior of the composite Fe 3 O 4 nanoparticles is reversible. For thinner grafted copolymer layer, it is irreversible. The P(NIPAm- co -TMSPMA) capped Fe 3 O 4 nanoparticles also exhibit superparamagnetic behavior. A linear relation between the saturation magnetization M s of copolymer-coated Fe 3 O 4 nanoparticles and the weight percent of grafted copolymer layer is first experimentally observed. With increasing the amount of grafted copolymer, M s of the Fe 3 O 4 nanoparticles decreases linearly.