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Preparation of Films of a Highly Aligned Lipid Cubic Phase

Squires, Adam M., Hallett, James E., Beddoes, Charlotte M., Plivelic, Tomás S., Seddon, Annela M.
Langmuir 2013 v.29 no.6 pp. 1726-1731
X-radiation, butanediol, coatings, crystallography, lipids
We demonstrate a method by which we can produce an oriented film of an inverse bicontinuous cubic phase (QIIᴰ) formed by the lipid monoolein (MO). By starting with the lipid as a disordered precursor (the L₃ phase) in the presence of butanediol, we can obtain a film of the QIIᴰ phase showing a high degree of in-plane orientation by controlled dilution of the sample under shear within a linear flow cell. We demonstrate that the direction of orientation of the film is different from that found in the oriented bulk material that we have reported previously; therefore, we can now reproducibly form QIIᴰ samples oriented with either the [110] or the [100] axis aligned in the flow direction depending on the method of preparation. The deposition of MO as a film, via a moving fluid–air interface that leaves a coating of MO in the L₃ phase on the capillary wall, leads to a sample in the [110] orientation. This contrasts with the bulk material that we have previously demonstrated to be oriented in the [100] direction, arising from flow producing an oriented bulk slug of material within the capillary tube. The bulk sample contains significant amounts of residual butanediol, which can be estimated from the lattice parameter of the QIIᴰ phase obtained. The sample orientation and lattice parameters are determined from synchrotron small-angle X-ray scattering patterns and confirmed by simulations. This has potential applications in the production of template materials and the growth of protein crystals for crystallography as well as deepening our understanding of the mechanisms underlying the behavior of lyotropic liquid-crystal phases.