title: Structural factors controlling the self-assembly of columnar liquid crystals.
abstract: A series of disc-shaped molecules were prepared by the condensation of 1,2-diamines with 2,3,6,7-tetrakis(hexyloxy)phenanthrene-9,10-dione to investigate the relationship between changes in molecular structure and the self-assembly of columnar liquid crystalline phases. A comparison of compounds with different core sizes indicated that molecules with larger aromatic cores had a greater propensity to form columnar phases, as did compounds substituted with electron-withdrawing groups. In contrast, molecules with electron-donating substituents were nonmesogenic. The clearing temperature of columnar phases increased linearly with the electron-withdrawing ability of the substituents, as quantified by Hammett sigma-values. The observed trends can be rationalized in terms of the strength of pi-pi interactions between aromatic cores in the liquid crystalline phases and suggest that both electrostatic interactions and dispersion forces play important roles in the self-assembly of these materials.
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: E Johan
authors.initials: EJ
authors.lastname: Foster
authors.forename: R Bradley
authors.initials: RB
authors.lastname: Jones
authors.forename: Christine
authors.initials: C
authors.lastname: Lavigueur
authors.forename: Vance E
authors.initials: VE
authors.lastname: Williams