NMR of solutes in nematic and smectic A liquid crystals: the anisotropic intermolecular potential

Abstract

Orientational order parameters determined from (1)H NMR spectroscopy of solutes in liquid crystals that form both nematic and smectic A phases are used to determine the solute smectic A order parameters and the smectic-nematic coupling term. For the analysis, it is necessary to know the nematic part of the potential in the smectic A phase: various ways of extrapolating parameters from the nematic phase to the smectic phase are explored.

Recent NMR Studies of Thermotropic Liquid Crystals

“…(101)) to the orientational order parameters for the twelve solutes at a single temperature in liquid crystals 1132, "MM", EBBA, and at three different temperatures of both 8CB and 8OCB spanning their N ranges [343]. The values obtained can be found in table 1 of a recent review [344]. For 1,2-dichlorobenzene (odcb) as an example, β odcb,zz (1) and β odcb,zz (2) are equal to À 0.927 and À 0.285, respectively, while β odcb,yy (1) and β odcb,yy (2) are 0.333 and 0.156, respectively in the two MS mechanisms.…”

“…(102) varying all free parameters (G L,ZZ (i), κ 0 L ðiÞ and τ 0 Ls ) with the expression: (103) failed to converge, and certain assumption seemed necessary in order to estimate the smectic effect. In this regard, the reader can refer to the review in which various strategies used in earlier studies have been discussed to estimate the mean nematic potential in the SmA phase [344]. Once the smectic Hamiltonian is in hand, the solutes' smectic order parameters τ s,i in a LC solvent is obtained using: …”