Chiral Correlation between Low-Birefringent Phases with Twist Grain Boundary-like Helix and Highly Birefringent Phases with Layer Chirality as Elucidated from Circular Dichroism Observations

The bent-shaped molecule with a central naphthalene core, 2,7-naphthalene-bis[4-(4-dodecylphenyliminomethyl)]benzoate, forms the low-birefringent B2 (LB-B2) phase with the twist grain boundary (TGB)-like helical structure and the low-birefringent B4 (LB-B4) phase in order of decreasing temperature. By applying the electric field, the LB-B2 phase is altered to the highly birefringent B2 (HB-B2) phase because of unwinding of the TGB-like helix. The HB-B2 phase is transformed to the HB-B4 phase without a loss of birefringence on cooling. These four phases show characteristic circular dichroism spectra, showing the consistent correlation through the transformation between these phases. The source of the chirality in the achiral system and the correlation in the chirality between these phases are discussed.