Elaboration and mechanical characterization of nanocomposites thin films - Part I: Determination of the mechanical properties of thin films prepared by in situ polymerisation of tetraethoxysilane in poly(methyl methacrylate)

The sol-gel process allows to design hybrid organic-inorganic materials constituted by organic molecules or macromolecules and inorganic metal oxo-polymers interpenetrated at the nanometer scale. These hybrids were deposited as functional coatings with tunable thickness on float glass substrates. Good adhesion and mechanical behaviour of the coatings are required to keep their functionality in time hence; the performance of the PMMA-SiO2 based thin films was investigated using nanoindentation. This study validates nanoindentation measurements as an appropriate technique to characterize hybrid organic-inorganic thin films, despite visco-clastic behaviours. Specific analysis procedures and the use of appropriate models allowed us to determine the indentation modulus and hardness of the hybrid layers reproductively. The structure and the mechanical behaviour are reported for thin films as a function of the fraction of silica. (c) 2004 Elsevier Ltd. All rights reserved.