Preparation and Characterization of Polymer TiO<sub>2</sub> Nanocomposites via <em>In-situ</em> Polymerization
Polymer nanocomposites are already a part of many important of worldwide businesses: automotive (molded part in cars), electronics and electrical engineering, household products, packaging industry, aircraft interiors, appliance components, security equipments. Among many nanocomposite precursors, TiO<sub>2</sub> nanopowder is increasingly being investigated due to its special properties. <br /><br /> The objective of this work is to synthesize and characterize polymer-TiO<sub>2</sub> hybrid nanocomposites. When dispersed at the nanoscale level TiO<sub>2</sub> could act as visually transparent UV filters and high-thermomechanical-performance materials. The synthesis strategy involved two steps. Firstly, aggregated TiO<sub>2</sub>, as received, was modified by 3-trimethoxysilyl propylmethacrylate aimed at altering its surface characteristics. The effect of modifier concentration on changing the physicochemical properties of TiO<sub>2</sub> surface was evaluated. Size distribution of unmodified and modified TiO<sub>2</sub> nanopowders was measured using a particle size analyzer. The qualitative and quantitative grafting of vinyl groups on TiO<sub>2</sub> surface was investigated with Fourier transform-infrared (FTIR) and proton nuclear magnetic resonance (<sup>1</sup>H-NMR) spectroscopy. Secondly, styrene monomer was then added to carry out copolymerization with vinyl groups on the modified TiO<sub>2</sub> by free radical initiator 2,2-azobis isobutyronitrile (AIBN) in bulk medium. FTIR spectra confirmed the formation of nanocomposites with polystyrene chains chemically linked to the surface of TiO<sub>2</sub> nanopowders. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated that the resulting nanocomposites displayed higher thermal stability and maintained similar glass transition temperatures (T<sub>g</sub>) compared with pure PS. Ultraviolet ?visible spectroscopy (UV-Vis) investigated that these nanocomposites have improved optical properties potentially acting as visually transparent UV filters. Such incremented properties were attributed to the nancoscale dispersion (20-50nm size) of TiO<sub>2</sub> into polystyrene matrix, which morphology was observed by scanning electron microscopy (SEM).