Reinforcement of nanostructured organogels by hydrogen bonds

Abstract

Organogels based on hydrogen-bond reinforced ordered micellar assemblies, having a very well-defined nanoscale structure and dynamic behaviour, are synthesized and investigated. The organogels consist of block copolymer micelles with covalently linked hydrogen bonding groups at their periphery which mediate attractive interactions between adjacent micelles. The structure and the viscoelastic properties of the organogels were systematically investigated by small-angle X-ray scattering and dynamic-mechanical measurements. We find with increasing number of hydrogen bonding groups an increase of the storage modulus, an increase of the melting temperature, and the development of a yield point. We show that the macroscopic viscoelastic properties of the organogels can be described by two theoretical models allowing a direct relation to the nanoscale organogel structure, the number of hydrogen bonds and the hydrogen bond lifetimes. The high-modulus transparent organogels undergo a reversible melting transition which allows them to be processed into well-defined micron-sized shapes.