title: Formation of complex self-assembled aggregates in non-ionic chromonics: dimer and trimer columns, layer structures and spontaneous chirality.
abstract: Dissipative particle dynamics (DPD) simulations are used to model the aqueous self-assembly of three variants of the non-ionic triphenylene-based chromonic mesogen, TP6EO2M. In the variants studied, one to three of the six methoxy poly(ethylene glycol) chains of TP6EO2M are replaced by short hydrophobic-lipophobic chains, causing a remarkable change in the structure of the mesophases formed. In the 100 wt% limit, corresponding to pure thermotropic phases, complex columnar phases arise, in which the underlying hexagonal packing is supplemented by additional order resulting from microphase separation of hydrophobic-lipophobic regions. With addition of water an array of novel chromonic phases are seen. In these phases supramolecular aggregates form in which hydrophobic-lipophobic chains are excluded from water by the joining together of single molecule chromonic stacks into dimers or trimers. These aggregates form chromonic N and M phases and, in the case of a "Janus mesogen" (with three hydrophobic-lipophobic chains on one side of the molecule), form a novel smectic chromonic phase. Spontaneous symmetry breaking is seen in columns composed of trimer stacks with defects. Here achiral molecular aggregates develop a spontaneous twist, inducing the formation of either left-handed or right-handed chiral aggregates. On the long time-scales accessible to DPD simulations, chiral aggregates are seen to be dynamic structures in which chirality inversion can take place over long periods of time.
authors.affiliation: Durham University, Department of Chemistry, Lower Mountjoy, South Road, Durham DH1 3LE, UK. mark.wilson@durham.ac.uk.
authors.forename: Martin
authors.identifier: http://orcid.org/0000-0003-1376-247X
authors.initials: M
authors.lastname: Walker
authors.affiliation: Durham University, Department of Chemistry, Lower Mountjoy, South Road, Durham DH1 3LE, UK. mark.wilson@durham.ac.uk.
authors.forename: Mark R
authors.identifier: http://orcid.org/0000-0001-6413-2780
authors.initials: MR
authors.lastname: Wilson