Influence of silane coupling agent on the properties of UV curable SiO2-PMMA hybrid nanocomposite

Abstract

This work reports the preparation of UV-curable organic–inorganic hybrid nanocomposites synthetized by sol–gel method with the aim of obtaining highly transparent anti-abrasive coatings with long-term storage and stability for the protection of organic light emitting diodes (OLEDs). The inorganic phase is composed of tetraethoxysilane (TEOS) condensed under acid catalysis and mixed with tetrafunctionnal acrylate monomer and oligomer. Vinyltriethoxysilane (VTES), 3-methacryloxypropyltrimethoxysilane (MEMO), and 3-mercaptopropyltriethoxysilane (MTMO) are used as silane coupling agent and hybrid network modifier. Among the various parameters influencing the structure and properties of the hybrid, this work focuses on the nature and amount of coupling agent and their influence in terms of transparency, mechanical properties, and stability of the formulation. An optimum can be found in the silica to coupling agent ratio. Low level of functionalization leads to hybrids displaying poor optical performances and stability due to the coalescence of silica domains. On the contrary, an excess of functionalization reduces the abrasion resistance and the silica network formation. Changing the organic pendant of coupling agents greatly influences the properties of the coating by promoting the organic–inorganic balance. Dense and flexible as well as mechanically resistant coatings can be obtained from similar formulation by simply tuning the nature of the coupling agent depending of the needs of the application.