Computer simulation of chiral liquid crystal phases. IV. Intermolecular chirality transfer to rotamers in a cholesteric phase

Abstract

Intermolecular chirality transfer was studied by investigating the conformational distribution of rotamers in a cholesteric guest-host phase using Monte Carlo (MC) simulations in the NVT ensemble. The guest-host system under investigation was given by N _c = 238 rigid, chiral Gay-Berne atropisomers as host molecules and N _a = 18 flexible Gay-Berne rotamers as guest molecules. The rigid, chiral Gay-Berne atropisomers of point symmetry group D₂ were defined by joining two Gay-Berne particles through a bond with a suitable fixed dihedral angle. The possibility of internal rotation about the bond axis without a rotational barrier was introduced as an internal degree of freedom for the guest molecules, for convenience denoted as Gay-Berne rotamers. Starting from an isotropic configuration, cholesteric phases were obtained on equilibrating the guest-host systems, whereby left-handed and right-handed cholesterics were formed depending on the M- and P-helicity of the atropisomers, respectively. Analysing the conformational distribution of the guest molecules in the cholesteric phase, we found an enantiomeric excess of rotamers of the guest molecules with the same helicity as the host molecules which is favoured on account of the intermolecular interactions in the cholesteric phase.