Superparamagnetic-Oil-Filled Nanocapsules of a Ternary Graft Copolymer

Abstract

Stearic and oleic acid-coated Fe₃O₄ nanoparticles were dispersed in decahydronaphthalene (DN). This oil phase was dispersed in water using ternary graft copolymer poly­(glycidyl methacrylate)-<i>graft</i>-[polystyrene-<i>ran</i>-(methoxy polyethylene glycol)-<i>ran</i>-poly­(2-cinnamoyloxyethyl methacrylate)] or PGMA-<i>g</i>-(PS-<i>r</i>-MPEG-<i>r</i>-PCEMA) to yield capsules. The walls of these capsules were composed of PCEMA chains that were soluble in neither water nor DN, and the DN-soluble PS chains stretched into the droplet phase and the water-soluble MPEG chains extended into the aqueous phase. Structurally stable capsules were prepared by photolyzing the capsules with UV light to cross-link the PCEMA layer. Both the magnetite particles and the magnetite-containing capsules were superparamagnetic. The sizes of the capsules increased as they were loaded with more magnetite nanoparticles, reaching a maximal loading of ∼0.5 mg of ligated magnetite nanoparticles per mg of copolymer. But the radii of the capsules were always <100 nm. Thus, a novel nanomaterialsuperparamagnetic-oil-filled polymer nanocapsuleswas prepared. The more heavily loaded capsules were readily captured by a magnet and could be redispersed via shaking. Although the cross-linked capsules survived this capturing and redispersing treatment many times, the un-cross-linked capsules ruptured after four cycles. These results suggest the potential to tailor-make capsules with tunable wall stability for magnetically controlled release applications