Nanocomposite coatings via simultaneous organic–inorganic photo‐induced polymerization: synthesis, structural investigation and mechanical characterization

Abstract

Hybrid sol–gel films were prepared via a simultaneous organic‐inorganic UV‐curing process using a diaryliodonium salt as a superacid photogenerator. In this single‐step procedure, an epoxy functionalized reactive resin mixed with a variable amount of either of two epoxy trialkoxysilane precursors was UV‐irradiated, causing both the initiation of epoxy ring‐opening copolymerization and the catalysis of trialkoxysilyl sol–gel reactions. The concomitant photo‐induced sol–gel process was found to have a significant effect on the two related propagation mechanisms in competition for the oxirane ring‐opening—the active chain‐end and the activated monomer mechanisms—as proved by a systematic examination of the hybrid material microstructure through 29Si and 13C solid‐state NMR spectroscopy. The effect of the oxo‐silica network generation on the epoxy reaction kinetics was also evaluated using real‐time Fourier transform infrared spectroscopy upon varying the epoxysilane structure and its concentration. Thermal and dynamic mechanical analyses were systematically performed on these hybrids, by studying thoroughly their structure–property interdependence. Other mechanical characterizations through tribological and scratch tests suggested that the present photopolymer–silica hybrid material provides a powerful tool to tailor mechanical property profiles. Copyright © 2010 Society of Chemical Industry

Cationic UV-Curing: Technology and Applications

“…The research group at Mulhouse demonstrated that organic–inorganic networks can be formed simultaneously in the presence of photogenerated acids that are able to catalyze the sol–gel process in the presence of the moisture in air. The authors showed that the diffusion of water originating from the atmosphere is sufficient to induce the hydrolysis of the alkoxysilane functions in the presence of the photogenerated acid.…”

Influence of actinic wavelength on properties of light-cured interpenetrating polymer networks

“…Therefore, at 395 nm, acrylate polymerization starts into a preformed epoxide network that promotes the entanglement between the two polymers and results in a narrow tan δ curve with one maximum. The lower T g value can be attributed to the fact that BA may increase chain termination by chain transfer mechanism . Shorter chains and a less crosslinked network could be created, although the acrylate and epoxide conversion remains high and comparable to the value obtained under UV irradiation.…”

Combination of radical and cationic photoprocesses for the single‐step synthesis of organic‐inorganic hybrid films

“…In equivalent systems based on epoxy trialkoxysilane involving a cationic process instead of a radical one, such a technique was remarkably useful to substantiate that hydroxyl‐containing byproducts of the sol–gel reactions had an impact on the polymerization mechanism. Methanol and water released in situ by hydrolysis and condensations reactions promoted a number of transfer reactions through an activated monomer mechanism,18, 42 thereby affecting the structure of the polymer backbone. In contrast, a radical polymerization is advantageous because it is unlikely to be affected by the sol–gel byproducts, owing to its insensitivity to hydroxylate species.…”