Truth about the origin of twist - a circular argument*

We examine emergent twist by applying both simulation and molecular theory to chromonic amphiphiles. Specifically, we study intrisically achiral particles: amphiphilic discotics in a solvent of spheres. While these systems exhibit a veritable zoo of hierarchical, chiral self-assembled structures, we restrict ourselves here to a set of parameterizations that lead to twisted bilayer structures. Here, we return to the elephant in the room – what causes and controls the supramolecular twist that develops in these systems? In considering this, we demonstrate that, while chirality is manifested at several levels in the twisted bilayers formed by amphiphilic chromonics, it originates from spontaneously-chiral preferred packing at a molecular level.

While this structural chirality sets the underlying template for the twist, stresses from the growth dynamics yield topological defects. There is surprisingly little sensitivity to molecular-level properties (unless they render the bilayer unstable with respect to an alternative aggregate). Thus, the emergence of a supramolecular pitch in these systems is demonstrated to be a many-body but molecular-scale process, founded on the stabilization of a packing-optimising chiral complex.