From the Molecular Structure to Spectroscopic and Material Properties: Computational Investigation of a Bent‐Core Nematic Liquid Crystal

Abstract

We present a computational investigation of the nematic phase of the bent-core liquid crystal A131. We use an integrated approach that bridges density functional theory calculations of molecular geometry and torsional potentials to elastic properties through the molecular conformational and orientational distribution function. This unique capability to simultaneously access different length scales enables us to consistently describe molecular and material properties. We can reassign (13)C NMR chemical shifts and analyze the dependence of phase properties on molecular shape. Focusing on the elastic constants we can draw some general conclusions on the unconventional behavior of bent-core nematics and highlight the crucial role of a properly-bent shape.

NMR of bent‐core nematogens: a mini‐review

“…It would appear that the ‘average’ A131 molecules belong to the ( Γ 1 , Γ 4 ) variety. This is consistent with the recent finding based on a molecular field theory that the molar fraction of ( Γ 1 , Γ 4 ) amounts to 90% at 395 K . As seen in the figure, the twist angles of rings ‘b’, ‘d’, and ‘e’ are relatively insensitive to the temperature over the nematic range, while despite rather large scatterings, ξ a of ring ‘a’ seems to show a pronounced change.…”

“…As seen in the figure, the twist angles of rings ‘b’, ‘d’, and ‘e’ are relatively insensitive to the temperature over the nematic range, while despite rather large scatterings, ξ a of ring ‘a’ seems to show a pronounced change. Recent DFT calculations indicated that ring ‘a’ has a wider angular distribution, as the potential barrier for rotations with respect to ring ‘b’ is low. Here, we see in Fig.…”

“…Ferrarini and coworkers have recently interpreted temperature behaviors of 13 C < δ i > in Fig. using a statistical approach . All Γ ( Γ 1 – Γ 4 ) conformers were considered in the SI model, which uses an adjustable parameter ε to reflect the orienting strength of the nematic environment.…”

Local Ordering at Mobile Sites in Proteins from Nuclear Magnetic Resonance Relaxation: The Role of Site Symmetry

“…38 Rhombic polar order-parameters have been invoked in the context of twist-bend nematic phases. 39 However, they have been associated with the conical angle and the pitch of the medium, rather than potentials formed of odd- L terms of eq 2. Potentials given by the L = 1, K = 0 term have been used to analyze dielectric relaxation of ferroelectric systems, 40 to treat electric-field-implied polar order, 41 and interpret the orientation of asymmetric paramagnetic molecules in strong magnetic fields.…”

Recent NMR Studies of Thermotropic Liquid Crystals

“…It seems conceivable that a N x phase can appear through stabilizing a uniaxial nematic system with local biaxial and polar cybotactic clusters by suitable purturbations such as surface treatment or an external field [79]. Ferrarini and coworkers have recently reinterpreted the temperature behaviors of 13 C chemical shifts previously reported in both nematic phases [287] using a statistical approach [293]. All Γ (Γ 1 ÀΓ 4 ) conformers together with chain conformers using Monte Carlo sampling were considered in the SI model, which used an adjustable parameter E to reflect the orienting strength of the nematic environment.…”