Red colored transparent PMMA–SiO 2 hybrid films

Abstract

Red colored transparent organic–inorganic hybrids films of a cross-linked polymethyl-methacrylate (PMMA) and silica were prepared via the sol–gel route using tetraethoxy-silane (TEOS) as precursor and a commercial organic red dye. 3-(Trimethoxysilyl) propyl methacrylate (TMSPM) was used to make compatible the organic and inorganic components of the precursor solution mixture. Four type of colored hybrid films were deposited using precursor solutions with the reactants molar ratio 1:0.5:1 for TEOS: TMSPM:MMA, respectively, and four different weight contents of the organic red dye. The hybrid films were studied by Fourier transform infrared spectroscopy, atomic force microscopy and optical transmission and reflection spectroscopy. The hardness of the films was determined from a pencil hardness test referred to ASTM Standard D 3363-92. The results showed that the colored hybrid films have a thickness of about 2 μm and consist of a homogeneous cross-linked organic–inorganic matrix with embedded dye molecules very well dispersed. The hardness of the hybrid films was enhanced with respect to that of the pure organic component. The AFM measurements showed very flat and smooth film surfaces with rms average roughness about 0.3 nm. The optical properties of the hybrid films including their color properties were determined from optical transmission and reflection spectroscopy. We found that the intensity of the color in the hybrid films and the corresponding color coordinates depend on the amount of red dye in the hybrid films. Photodegradation studies were performed by monitoring the optical density of the films as a function of the exposure time to illumination for several values of illumination intensity.