(346e) Synthesis and Characterization of Environmentally Responsive Superparamagnetic Nanoparticles

We have synthesized magnetite nanoparticles with temperature- and pH- sensitive polymer coating through surface-initiated atom transfer radical polymerization (ATRP). The core, superparamagnetic magnetite (Fe3O4) nanoparticles, was synthesized as follows. A solution of Fe(II)/Fe(III) ions, obtained from a mixture of FeCl2.4H2O and FeCl3.6H2O with a molar ratio of 1:2 at pH 11-12 is stirred under nitrogen purging for 30 minutes. TEM micrographs show nanoparticles of size range ~ 10 nm and VSM confirms their superparamagnetism.

Polymer coating of the nanoparticles involved firstly self-assembly of a monolayer of ATRP initiator onto magnetite surface. Subsequently, aqueous copolymerization at room temperature of t-butyl acrylate (tBAA) and N-isopropylacrylamide is carried out to form (tBAA-b-NIPAM) brushes. tBAA blocks were then converted to acrylic acid (AAc) blocks through normal hydrolysis procedures. Characterization of the polymer brushes (i.e. molecular weight and polydispersity) was done by gel permeation chromatography. Temperature and pH dependency of the LCST (lower critical solution temperature) of the grafted polymer brushes were investigated using laser light scattering (hydrodynamic size) and UV-VIS spectrophotometer (turbidity). It was found that pH effect on LCST scales with the amount of ionizable acrylic acid moieties on the polymer coating. Additional polymer blocks may be added to the coating for interaction with various biomolecules, such as proteins. Application to protein purification and various biomedical fields will be investigated.