Structures in optically isotropic and bluish colored cubic phases formed by enantiomeric association in an (R,S) dichiral compound and a stereoisomeric (R,R) and (S,S) mixture

Abstract

The structures of an optically isotropic cubic phase and a bluish colored phase exhibited in an (R,S) dichiral compound with fluorines have been investigated. Not only the bluish colored phase but also the cubic phase exhibit circular dichroism, being confirmed to be chiral phases. Based on the analysis of several X-ray diffraction peaks observed in the small angle range, we find that the optically isotropic chiral cubic (IsoX) phase belongs to the symmetry group I432. It is also found that the cubic phase emerging in the equimolar mixture of (R,R) and (S,S) stereoisomers also has I432 symmetry, suggesting the formation of the cubic phase due to chiral recognition between chiral end chains. The molecular recognition upon forming the IsoX phase is also discussed by mixing (R,R) and (S,S) stereoisomers in the crystalline phase. The other important finding is the exotic phase with a blue colored and foggy texture below the isotropic liquid. X-Ray diffraction results in this phase clearly show a diffraction ring corresponding to a layer structure with a quite long correlation length. We assigned this phase to a smectic blue phase (BPsm).