Mesostructured silica hybrids from liquid polyelectrolyte–surfactant–aminosilanol complexes

Abstract

A novel approach involving the use of a pre-hydrolysed aminosilanol to induce the fluidization of solid-like polyelectrolyte–surfactant complexes to produce viscous liquids that can be processed into mesostructured silica hybrids or electrospun fibres is described. Polyelectrolyte–surfactant–aminosilanol (PSA) complexes were prepared in aqueous mixtures of anionic poly(acrylate) (PA), cationic cetylpyridinium (CP) chloride and cationic pre-hydrolysed 3-aminopropyltriethoxysilane (HAPTES). Increasing the concentration of HAPTES in the mixture changed the phase state of the PSA product from a white precipitate to a liquid complex exhibiting Newtonian behaviour. This was attributed to the partial replacement of bound CP by HAPTES molecules at carboxylate sites on the PA chains. Binding studies indicated that the onset of liquid PSA-complex formation occurred at a HAPTES binding level of approximately 0.3. Fluidization of the solid-like PA–CP complexes by addition of HAPTES was exploited for the preparation of polyelectrolyte–surfactant–silica hybrids with hexagonal or lamellar mesostructure via evaporation-induced assembly. The high viscosity of the PSA liquids was also used to prepare mats of polyelectrolyte–surfactant–silica hybrid micro-fibres by direct electrospinning of the liquid complexes.