Red colored transparent PMMA–SiO 2 hybrid films J.L. Almaral-Sa ´nchez a,b , E. Rubio c,d , A. Mendoza-Galva ´n a , R. Ramı ´rez-Bon a, * a Centro de Investigacio ´n y Estudios Avanzados del IPN. Unidad Quere ´taro, Apdo. Postal 1-798, 76001 Quere ´taro, Qro., Me ´xico b Universidad Auto ´noma de Sinaloa, Fuente de Poseido ´n y Prol. Angel Flores, S.N., C.P. 81200, Los Mochis Sin., Me ´xico c Centro de Fı ´sica Aplicada y Tecnologı ´a Avanzada, UNAM, A.P. 1-1010 Quere ´taro Qro. 76000, Me ´xico d Centro Universitario de Vinculacio ´n, BUAP, 29 Oriente 601-1, Col. Ladrillera de Benı ´tez, C.P. 72540, Puebla, Pue., Me ´xico Received 23 November 2004; revised 30 May 2005; accepted 22 June 2005 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 mm 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. q 2005 Elsevier Ltd. All rights reserved. Keywords: A. non–crystalline materials; B. Sol–gel growth; D. Microstructure; D. Optical properties 1. Introduction Hybrid sol–gel derived materials are very versatile materials which combine the complementary properties of the inorganic and organic materials which constitute them [1–7]. The actual availability of a great number of precursors for the inorganic component through metal alkoxides, organo(alkoxi)silanes and nanoparticles and their compatibility to the incorporation of polymerizable groups such as methacryloxy, vinil and epoxy groups, yield to the possibility to obtain a wide variety of hybrid sol gel derived materials [1–4,7–15]. This type of materials are mainly used as coating for different purposes but recently also as bulk materials. They consist of a dual polymer network, in which cluster or polymer type inorganic structures are linked to organic groups or polymer fragments [1,10]. The hybrid networks can be conveniently divided in two general classes. Class I corresponds to hybrid systems, where organic molecules, oligomers, or low molecular weight organic polymers are simply embedded in an inorganic matrix. Both components exchange rather weak bonds, mainly through van der Waals, hydrogen, or ionic interactions. Class II corresponds to hybrid organic–inorganic com- pounds, where organic and inorganic components are bonded through stronger covalent or ionic- covalent chemical bonds [2,4,5]. Novel and multiple purpose hybrid materials can be obtained by choosing appro- priately the inorganic and organic components with the adequate composition [2,4]. These materials have found technological applications in scratch and abrasion resistant coatings for plastics, corrosion protective Journal of Physics and Chemistry of Solids 66 (2005) 1660–1667 www.elsevier.com/locate/jpcs 0022-3697/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpcs.2005.06.006 * Corresponding author. E-mail address: rrbon@qro.cinvestav.mx (R. Ramı ´rez-Bon).