Thermal Properties of PMMA/TiO2 Nanocomposites Prepared by In-Situ Bulk Polymerization

The surface of anatase TiO2 nanoparticles, obtained by the controlled hydrolysis of titanium tetrachloride, was modified by 6-palmitate ascorbic acid. The surface modified TiO2 nanoparticles were dispersed in methyl methacrylate and mixed with a appropriate amount of poly(methyl methacrylate) to obtain a syrup. The nano-composite sheets were made by bulk polymerization of the syrup in a glass sandwich cell using 2,2'-azobisisobutyronitrile as initiator. The molar masses and molar mass distributions of synthesized poly(methyl methacrylate) samples were determined by gel permeation chromatography. The content of unreacted double bonds in synthesized samples was determined by H-1 NMR spectroscopy. The influence of TiO2 nanoparticles on the thermal stability of the poly(methyl methacrylate) matrix was investigated using thermogravimetric analysis and differential scanning calorimetry. The synthesized samples of poly(methyl methacrylate) have different molar mass and polydispersity depending on the content of the surface modified TiO2 nanoparticles. The values of glass transition temperature of so prepared nanocomposite samples were lower than for pure poly(methyl methacrylate), while the glass transition temperature of samples preheated in inert atmosphere was very similar to the glass transition temperature of pure poly(methyl methacrylate). The thermal stability of nanocomposite samples in nitrogen and air was different from thermal stability of pure poly(methyl methacrylate). POLYM. COMPOS., 30:737-742, 2009. (C) 2008 Society of Plastics Engineers