The helicoidal modulated nematic phases in a model system of V-shaped molecules

Abstract

The phase behavior of the melt of the symmetric V-shaped molecules has been inspected within the Landau–de Gennes approach. The arms of V-shaped molecule are modeled by rod-like segments connected at an external angle [Formula: see text]; these segments are assumed to be composed of monomer units. The phase diagram of the system contains regions of stability of the isotropic, homogeneous nematic, and modulated nematic phases: nematic twist bend (N[Formula: see text]) phase that is characterized by the three directors which move on a helix and one of these directors forms a fixed nonzero cone angle with the helix axis, and the N0 modulated phase in which one director is parallel to the helix axis while two others are orthogonal to the helix axis. The characteristic periods of modulated structures were found to be of order a few molecular lengths.