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Experimental Confirmation of Transformation Pathways between Inverse Double Diamond and Gyroid Cubic Phases

Seddon, Annela M., Hallett, James, Beddoes, Charlotte, Plivelic, Tomás S., Squires, Adam M.
Langmuir 2014 v.30 no.20 pp. 5705-5710
X-radiation, coatings, geometry, lipids, nanomaterials, osmotic stress, polyethylene glycol
A macroscopically oriented double diamond inverse bicontinuous cubic phase (QIIᴰ) of the lipid glycerol monooleate is reversibly converted into a gyroid phase (QIIᴳ). The initial QIIᴰ phase is prepared in the form of a film coating the inside of a capillary, deposited under flow, which produces a sample uniaxially oriented with a ⟨110⟩ axis parallel to the symmetry axis of the sample. A transformation is induced by replacing the water within the capillary tube with a solution of poly(ethylene glycol), which draws water out of the QIIᴰ sample by osmotic stress. This converts the QIIᴰ phase into a QIIᴳ phase with two coexisting orientations, with the ⟨100⟩ and ⟨111⟩ axes parallel to the symmetry axis, as demonstrated by small-angle X-ray scattering. The process can then be reversed, to recover the initial orientation of QIIᴰ phase. The epitaxial relation between the two oriented mesophases is consistent with topology-preserving geometric pathways that have previously been hypothesized for the transformation. Furthermore, this has implications for the production of macroscopically oriented QIIᴳ phases, in particular with applications as nanomaterial templates.