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Sol-gel derived unsupported films and thin rods have been obtained from co-hydrolysis of triethoxysilane and methyldiethoxysilane. The materials are flexible, dense and transparent. Films and rods have been aged for different periods of time in air at room temperature. The elastic modulus has been measured by means of tensile or flexural tests. Measurements showed an increase of elastic modulus with aging time and showed different values for films and rods. The observed evolution of mechanical properties has been related to a corresponding structural modification as highlighted mainly by MAS-NMR studies. Analyses pointed out the crucial role of condensation processes and showed that the stiffness increase arises from the formation of relatively few bonds which link and constrain pre-existing mobile network regions.

This paper deals with the production and characterization of nano-structured UV curable acrylic coatings applied on mild steel substrates for corrosion protection purposes. UV curable acrylic coatings were modified in two ways: by adding pre-formed silica nanoparticles modified with MEMO molecules and by promoting an in situ formation of silica domains functionalized with MEMO molecules. The coatings were characterized by means of both chemical (FT-IR, DSC, UV-Vis absorbance, Gloss) and electrochemical techniques (EIS, Potential vs Time). The coatings showed different thermal stability as revealed by the DSC measurements. The coatings showed also different barrier properties depending on the presence of the nanoparticles or of the silica domains. It was proved that a convenient functionalization of the silica domains (or particles) lead to noticeable improvements of the barrier properties of the coating respect to the pure UV curable polymer.