Electrostatic vs. covalent bond in modified Jeffamine: effect on the phase behaviour and on the templating of mesoporous silica

Abstract

Ionic and covalent combinations of oleic acid and Jeffamine ED900, a homoditopic polyetheramine, lead to novel porogens, either "cataniomeric" or nonionic surfactants, bearing respectively ammonium/carboxylate ionic pairs and/or amidic bonds. The effect of the electrostatic interaction vs. the covalent bond at the molecular level is clearly evidenced by the differences in the self-assembling behaviour, in either micellar or liquid crystal domains. Organized mesoporous materials were prepared through the cooperative templating mechanism from micelles and a silica source. The optimal reaction conditions were different for the nonionic (A) and di-ionic (B) surfactants, and the resulting materials had various morphologies (rod-like vs. spheres) and pore sizes (4 vs. 14 nm). Interestingly, the hybrid surfactant exhibits a versatile behaviour regarding the silica formation, acting as either a nonionic or a di-ionic surfactant in its respectively optimal conditions, A or B. This behaviour highlights the uniqueness of dynamic micelles as a novel supramolecular tool for the design of tailored mesoporous materials and could represent a novel platform for the design of pH responsive controlled drug delivery systems.