AVS 52nd International Symposium
    Nanometer-Scale Science and Technology Monday Sessions
       Session NS2-MoA

Paper NS2-MoA5
Submicron Dispersions from Urea-Based Liquid Crystalline Phases

Monday, October 31, 2005, 3:20 pm, Room 210

Session: Nanometer Scale Assembly
Presenter: C. Fong, CSIRO Molecular Science, Australia
Authors: C. Fong, CSIRO Molecular Science, Australia
J. Booth, RMIT School of Applied Sciences, Australia
C.J. Drummond, CSIRO Molecular Science, Australia
I. Krodkiewska, CSIRO Molecular Science, Australia
D. Wells, CSIRO Molecular Science, Australia
P.G. Hartley, CSIRO Molecular Science, Australia
Correspondent: Click to Email
Surfactant self assembly phases such as micelles, vesicles / liposomes, and lyotropic mesophases are of technological importance as carriers for cosmetic formulations, as drug delivery systems, and as protein crystallisation media. Lyotropic mesophases offer particular advantages since under certain conditions they are robust to dilution, temperature and composition. The three dimensional structure also enhances solubilisation of hydrophilic and/or hydrophobic moieties when compared to their liposomal analogues. There are currently a limited number of materials which exhibit dilutable mesophase behaviour. Our aim was to design surfactants capable of self assembling into higher order surfactant liquid crystalline phases, which would be stable to dilution over a broad temperature range. In this study we have explored the urea based surfactants since the conventional wisdom suggested that this class of compounds was unable to form liquid crystalline phases. This work negates this long held view and demonstrates for the first time that surfactant mesophases with the urea head group are favoured by highly splayed hydrophobes with exaggerated cross sections. Hydrophobes such as hexahydrofarnesyl and phytanyl were successful in promoting room temperature inverse hexagonal phases which are stable against dilution and robust for a large temperature and composition regime. The current synthesis strategy has therefore more than doubled the previously known numbers of compounds with these properties. Colloidal dispersions of the bulk inverse hexagonal phase were prepared with average particle size < 300 nm. These nanoparticles have much reduced viscosities over the bulk phase with high surface area and the benefit that the bulk structure has been preserved. Significantly, they are of a suitable size range for applications such as intravenous drug delivery or bioremediation.