Investigation into the nanostructural evolution of TiO2–polymethyl methacrylate nanohybrids derived from the sol–gel technique

In this research, the nanostructural evolution of TiO2 crystallite upon in situ sol−gel process of titania–polymethyl methacrylate (TiO2–PMMA) nanocomposites was systematically nvestigated.
The main objective is to understand the mechanisms responsible for the amorphous nature of the sol−gel derived TiO2−polymethyl methacrylate (PMMA) nanohybrids. For this purpose, two sol−gel parameters i.e. the coupling agent concentration, water content or hydrolysis ratio (rw), and pH value of the titania precursor solution were varied. On the basis of XRD analysis, it has been found that the modification of those parameters can enhance the nanocrystallinity of pure TiO2 phase. However, this could not be applied when the titania precursor was mixed with the PMMA segment. On the basis of XRD and FTIR analyses, it was found that the largely amorphous TiO2 state is related to the fast development of stiff Ti−OH networks during the hydrolysis and condensation stages in sol−gel process, worsened by the entrapment of the rigid PMMA matrix.