Molecular organogels of the sodium salt of ( R)-12-hydroxystearic acid and their templated syntheses of inorganic oxides

Abstract

( R)-12-Hydroxystearic acid (HSA), a natural product from castor oil, is a well-known low-molecular mass organogelator (LMOG). Here, we demonstrate that the sodium salt of HSA, HSA-S, is an extremely versatile and efficient LMOG. Furthermore, its self-assembled fibrillar networks (SAFINs) in gels with ethanol, benzene, tetrahydrofuran, and dimethyl sulfoxide, as well as the gel of HSA with benzene, are shown to act as templates during the sol–gel polymerization of tetraethyl orthosilicate (TEOS) in the absence or presence of an external catalyst. The templated, fiber-like objects obtained after calcinations have been characterized. The shape of the templated silica is strongly influenced by the catalyst applied. In addition, it has been possible to effect the formation of assemblies of nanoscale objects of Fe 2O 3 and CuO by polymerization of appropriate precursors in HSA-S based gels and in suspensions, respectively, followed by drying and calcination. The procedures employed are efficient and inexpensive protocols to make porous nanomaterials using organogels. Typically, templated syntheses of such materials in organogels have employed less accessible and more structurally complex LMOGs than HSA-S or HSA. Electrostatic interactions via Na + bridges or H-bonding between silicate intermediates and gelator strands are proposed to be a primary driving force for templating.