Synthesis and characterization of poly(styrene-co-fluorescein O-methacrylate)/poly(N-isopropylacrylamide)-Fe₃O₄ core/shell composite particles

We demonstrate the synthesis and characteristics of multifunctional poly(styrene-co-fluorescein O-methacrylate)/poly(N-isopropylacrylamide)-Fe ₃O₄ [P(St/FMA)/PNIPAAm-Fe₃O₄] core/shell composite particles, in which the core consists of fluorescent materials and the shell consists of magnetic and thermo-responsive components. First, core/shell particles consisting of a fluorescent P(St/FMA) core and thermo-responsive PNIPAAm-rich shell were prepared by two-stage shot-growth emulsion polymerization. Next, Fe₃O₄ nanoparticles were immobilized via electrostatic interactions and then covalently linked to the shell via surface coordinated Aphen by a coupling reaction in order to obtain magnetic properties. The morphology of P(St/FMA)/PNIPAAm-Fe₃O ₄ composite particles, confirmed by transmission electron microscopy (TEM), reveals that Fe₃O₄ nanoparticles are located in the PNIPAAm shell. The thermo-sensitivity of composite particles to hydrodynamic diameter was confirmed by using dynamic light scattering (DLS). Photoluminescence (PL) spectra indicate that the fluorescence emission intensity of core/shell particles is highly sensitive to the pH of an aqueous medium. The core/shell composite particles exhibited a combination of fluorescent, magnetic, pH and thermo-responsive behavior.