UV curable cycloaliphatic epoxy functionalized oligosiloxane resin is synthesized by non-hydrolytic sol–gel reaction for application in encapsulation of organic light emitting devices (OLEDs). The physical and chemical properties of polymerized cycloaliphatic epoxy hybrid materials (hybrimers) are easily tunable by controlling the precursors. A single hybrimer coating on a PET film is optically transparent and shows low permeability of up to 0.68 g m−2 day−1 per mil measured by a Ca degradation test. It is found that the permeability is influenced by the siloxane and epoxy network density, and the surface energy of the coating. An optimized hybrimer barrier coated film is applied to the encapsulation of an OLED with the aim of extending life-time.

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High performance organic-inorganic hybrid barrier coating for encapsulation of OLEDs

Kinetic study of methyltriethoxysilane (MTES) hydrolysis by FTIR spectroscopy under different temperatures and solvents

This study explored the effectiveness of tetraethyl orthosilicate (TEOS) as a Portland cement mortar consolidant to verify whether it meets the requirements for use in cultural assets. TEOS was found to raise cement mortar strength, lower its porosity and permeability and occasion minimal alteration in its appearance, an indication of its suitability to conserve heritage mortar works. FTIR and 29Si MAS NMR studies supported the notion that TEOS interacts with the hydrated phases of the cement, portlandite and C–S–H gel. The reaction product between portlandite and TEOS was C–S–H gel and between TEOS and C–S–H gel was a gel with longer chain.

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Interaction of TEOS with cementitious materials: Chemical and physical effects

In this work we present the development of a nanocomposite material composed by silica nanoparticles in a hybrid organic–inorganic sol–gel matrix for corrosion protection of aluminium alloys. The sol–gel matrix was produced from an inorganic precursor, tetraethoxysilane (TEOS), a hybrid precursor organically functionalized with C C groups, 3-metacryloxypropyltrimethoxysilane (MPS), and an organic bi-functional monomer, ethyleneglycol-dimethacrylate (EGDMA) used to increase the cross-linking network. Silica nanoparticles, on the other side, increase the density and provide a major mechanical performance through the reinforcement of the coating. The evolution of the sol, mainly the chemical structure, during the processes of hydrolytic condensation and organic polymerisation was studied as a function of the sol concentration through Fourier transformed infrared spectroscopy (FTIR), rheometry, laser diffraction analysis and contact angle. Mono and multilayer coatings were deposited by dipping onto AA 2024 substrates and characterised by profilometry. The corrosion behaviour was followed through potentiodynamic tests and Electrochemical Impedance Spectroscopy (EIS).

Improved corrosion resistance of AA2024 alloys through hybrid organic–inorganic sol–gel coatings produced from sols with controlled polymerisation

The initial molecular steps of the acid-catalyzed silica sol-gel process departing from tetraethylorthosilicate (TEOS) were investigated by in situ Si-29 NMR and UV-Raman spectroscopy. The use of a substoichiometric H2O:TEOS molar ratio (r-value 0.2-1.2) slowed the silicate oligomerization reaction and allowed unraveling the initial steps of silica condensation. Molecular modeling confirmed Raman signal and Si-29 NMR shift assignment. A comprehensive listing of all Raman and Si-29 NMR assignments is provided, including unique Raman assignments of cyclosilicates and the linear tetramer. The combination of experiment and modeling allowed an analysis of the reaction kinetics. The derived kinetic model and the experimental observation both revealed that the H2O:TEOS molar ratio had a strong influence on the reaction kinetics but not on the reaction pathways. The multianalytical approach led to development of an oligomerization scheme. As dominant oligomerizations, chain growth, cyclodimerization, and branching were identified. Under the investigated conditions, chains did not grow longer than pentamer, and ring sizes were limited to 6-rings. Chains of 4 Si atoms and 4-rings were abundant species. Branched rings and chains were formed by attachment of dimers and trimers. Gelation proceeded from branched 4-rings and branched chains with limited hydroxyl functionalities.

Jean-Claude Bureau

Papers

Spectroscopic study of TMOS–TMSM–MMA gels: Previously identification of the networks inside the hybrid material

Surface model of formation of silicon nitride on monocrystalline silicon

Physico-Chemical Properties of an Hybrid Glass