Structuring of Alkyl-Triazole Bridged Silsesquioxanes

Abstract

Non-porous bridged silsesquioxanes (BSs) were produced by sol-gel reactions and self-directed assembly, in the presence of an acid catalyst and a large excess of water, from bridged organosilane precursors (BOPs) synthesized by click chemistry. The rational design of the compounds, comprising an amine group and alkyl chains with variable length (n), pendant and anchored on a single position to a triazole ring, and the control of acid content (w, moles of acid per moles of BOP) enabled the tuning of the morphology and structure of the BSs. At n=6, 12 and 16, and w=0.2 amorphous hybrids were produced as uniform isotropic micro- to nanospheres. Structuring resulted at n =16 and w=1.2 or n=20 and w=0.2, yielding lamellar bilayer structures. In the case of the BS with n=20 and w=1.2 a lamellar bilayer phase and a minor hexagonal 2D structure emerged. The quite unusual formation of the latter structure was attributed to the presence of a chloride ion close to the proton located between the N(2) atom of the triazole ring and the amine group of the organic spacer, acting as a curvature agent.