Mixed Columnar Assembly of Ferroelectric and Antiferroelectric Benzene Derivatives Bearing Multiple -CONHC14H29 Chains.

Abstract

The discotic hexagonal columnar (Colh) liquid crystalline phases of simple benzene derivatives bearing -CONHC14H29 chains at the 1-, 3-, and 5-positions (3BC) and 1-, 2-, 4-, and 5-positions (4BC) display ferroelectricity and antiferroelectricity, respectively. The phase transition behavior, molecular assembly structures, dielectric response, and ferroelectric properties of their mixed crystals [(3BC)1-x(4BC)x] were evaluated to clarify the nanoscaling effect on the collective inversion of the one-dimensional (1D) N-H···O═ hydrogen bonding interaction observed in the (3BC)∞ chain. A small quantity of 4BC doped into 3BC (x ≤ 0.03) maintained the ferroelectric polarization-electric field response (P-E) in the (3BC)1-x(4BC)x chains, where the antiferroelectric 4BC molecules in the ferroelectric 3BC column act as a pinning potential site for dipole inversion. On the contrary, a relatively large amount of 4BC doping (x ≥ 0.1) forms a domain separation state between the hydrogen-bonded (3BC)∞ and (4BC)∞ columns, in which the ferroelectric P-E hysteresis completely disappeared. The correlation length for the appearance of ferroelectricity in the 1D column was estimated to be ∼40 nm in the Colh liquid crystalline phase of 3BC.