Eur. Phys. J. E (2012) 35: 112
https://doi.org/10.1140/epje/i2012-12112-0

Regular Article

Smectic order parameters via liquid crystal NMR spectroscopy: Application to a partial bilayer smectic A phase

¹ Dipartimento di Chimica, Università della Calabria, Campus di Arcavacata, Via Pietro Bucci Cubo 12C, I-87036, Rende (Cosenza), Italy
² Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, D-69120, Heidelberg, Germany
³ Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Campus de Cantoblanco, E-28049, Madrid, Spain

^* e-mail: giorgio.cinacchi@uam.es

Received: 13 April 2012
Revised: 5 July 2012
Accepted: 5 October 2012
Published online: 29 October 2012

Abstract

Solute molecules were dissolved in the liquid crystal 4-cyano-4′-n-octyloxybiphenyl (8OCB), known to form a partial bilayer smectic-A phase. Through measurement of solutes’ and solvent’s orientational order parameters via nuclear magnetic resonance spectroscopy, and their analysis via a statistical thermodynamic density functional theory, values of the solvent’s positional order parameters and solutes’ positional-orientational distribution functions were obtained. Near to the transition to the nematic phase, the main positional order parameter of the smectic liquid crystal turned out to be comprised in the interval 0.4–0.6, though the quality of the fittings assuming the phase as nematic all across the temperature range investigated was only slightly worse. This may be ascribed to the looseness of the partial bilayer smectic structure. Solutes were found to preferentially lie in those regions where liquid crystal molecule terminal chains are located.