Template-directed self-assembly by way of molecular recognition at the micellar–solvent interface: modulation of the critical micelle concentration

Abstract

By incorporating the concepts of structural preorganisation and complementarity in concert with non-covalent donor-acceptor [ππ] and hydrophobic interactions, a duo of π-electron deficient bipyridinium-based linear and gemini amphiphiles capable of responding to molecular templation have been designed and synthesised. When combined with π-electron rich di(ethylene glycol)-disubstituted 1,5-dihydroxynaphthalene, a dramatic decrease in the critical aggregation concentration by ≈66% was observed with concomitant increases in the hydrodynamic diameter, ζ-potential, and Langmuir surface pressures of the micellar solutions-thus enhancing the detergents' efficiency and effectiveness at lowering the surface tension of water. By employing a phase separation model that takes into account the degree of counterion binding to the micellar aggregate superstructure, the effects of donor-acceptor templation on the Gibb's free energy of micellisation (ΔG) for the amphiphiles was quantified. It was found that donor-acceptor templation was capable of lowering ΔG by up to 1.75 kcal mol(-1) at which point it was observed, while under the influence of molecular templation, that linear single hydrophobic tailed detergent molecules exhibit properties characteristic of double-tailed phospholipid-like gemini surfactants.