Twists and Turns in Bicontinuous Cubic Phases

We recently reported ^[1] that all compounds, when in the triple-network cubic liquid crystal phase with Im-3m symmetry ^[2] (now considered possibly I432) display strong optical activity, even though the compounds themselves are intrinsically not chiral. In contrast, the double gyroid cubic phase Ia-3d is never optically active. We have explained these intriguing observations by a twist around the axis of network segment and a long-range propagation of chiral sense through chirality matching at network junctions. ^[1] The absence of net chirality in the Ia-3d phase was attributed to cancelation between the two antichiral networks. Now we report on another bicontinuous phase that contains two isochiral networks which therefore has high net chirality, whether or not it contains chiral molecules. We will also report on the remarkable effects of chiral environment on the nucleation and the domain shape of these phases due to the high barrier to helix reversal.

1. C. Dressel, F. Liu, M. Prehm, X.B. Zeng, G. Ungar, C. Tschierske “Dynamic mirror-symmetry breaking in bicontinuous cubic phases”, Angew. Chem. Int. Ed., 2014, 53, 13115 –13120.
2. XB Zeng, G Ungar, M Impéror-Clerc, “A Triple-Network Tricontinuous Cubic Liquid Crystal”, Nat. Mater., 2005 4 562-567.