pH-Responsive Bridged Silsesquioxane

A pH-responsive bridged silsesquioxane was obtained via the sol−gel process from a bis-silylated triazine derivative bearing a triple DAD (donor−acceptor−donor) moiety which was strongly hydrogen-bonded to the three ADA (acceptor−donor−acceptor) sites of cyanuric acid. The latter template molecule was easily removed from the resulting hybrid material upon acidic treatment, which yielded the template-free bridged silsesquioxane with preserved morphology and unaltered particle size as demonstrated by SEM. As expected, the surface area of the acid-treated hybrid was significantly higher than that of the untreated material, as demonstrated by nitrogen adsorption measurements. The absence of cyanuric acid in this material was confirmed by solid state NMR and by IR. It was shown that a mild acidic medium (pH = 5.5) is sufficient to release the cyanuric acid template, thus providing a novel route to new hybrid materials with potential applications as efficient carriers for pH-responsive delivery systems.