Grafting of titanium dioxide microspheres with a temperature-responsive polymer via surface-initiated atom transfer radical polymerization without the use of silane coupling agents

Abstract

Titania microspheres with narrow size distribution and diameters of about 1 µm were prepared and subsequently functionalized using surface-initiated atom transfer radical polymerization (ATRP) of N-isopropylacrylamide. The ATRP initiator was immobilized on the particle surface via acylation of surface hydroxyl groups with α-bromoisobutyryl bromide. Subsequently, an established ATRP reaction system was used for the preparation of titania surface-grafted poly(N-isopropylacrylamide) (PNiPAAm). Characterization was performed with electron microscopies, X-ray diffraction, infrared spectroscopy and dynamic light scattering. It was found that the particle size in aqueous dispersions changed reversibly with temperature as expected for a shell of PNiPAAm, a polymer with a lower critical solution temperature at 32 °C. This confirmed the successful preparation of functional, stimuli-responsive TiO2 microparticles via a straightforward controlled surface-initiated polymerization method.