Temperature-Responsive Nanocomposites Based on Mesoporous SBA-15 Silica and PNIPAAm: Synthesis and Characterization

Thermosensitive nanocomposites based on mesoporous SBA-15 silica and poly(N-isopropylacrylamide) (PNIPAAm) have been synthesized via in situ polymerization of monomers deposited on the pore walls. The introduction of monomers and polymerization were examined by Fourier-transform infrared spectroscopy (FT-IR). The structures and properties of the composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2 adsorption-desorption, thermogravimetric analysis (TG), and differential scanning calorimetry (DSC). It was demonstrated that the polymerization initiated by free radicals occurred within the channels of SBA-15, and the polymer layer fixed by the penetration of polymer chains into the complementary pores was formed on the pore walls. The distribution and uniformity of the polymer coating along the channel walls depend on the content of polymer in the composite, which can be controlled by altering the monomer/SBA-15 mass ratio in the synthesis. Higher polymer content gives rise to mesopores plugged partly but does not alter the ordered hexagonal mesostructure of the material. Moreover, the thermosensitive property of PNIPAAm is retained in the naonocomposites, which have a lower critical solution temperature (LCST) close to that of pure PNIPAAm.