Publication Title

Physical Review E

Publication Date

5-15-2010

Document Type

Article

DOI

10.1103/PhysRevE.81.051706

Keywords

Dielectric Inversion Frequency, Liquid Crystal, Phase, Order, Nmr, Transitions, Mesogens

Disciplines

Physics

Abstract

The results of a recent investigation of the nematic biaxiality in a bent-core mesogen (A131) are in apparent disagreement with earlier claims. Samples of mesogen A131 used in the two studies were investigated with polarized optical microscopy, conoscopy, carbon-13 NMR, and crossover frequency measurements. The results demonstrate that textural changes associated with the growth of biaxial nematic order appear at similar to 149 degrees C. The Maltese cross observed in the conoscopic figure gradually splits into two isogyres at lower temperatures indicating phase biaxiality. Presence of the uniaxial to biaxial nematic phase transition is further confirmed by temperature trends of local order parameters based on (13)C chemical shifts in NMR experiments. Frequency switching measurements also clearly reveal a transition at 149 degrees C. Differences between the two reports appear to be related to the presence of solvent, impurities, and/or adsorbed gases in samples of A131 used in the study of Van Le et al. [Phys. Rev. E 79, 030701 (2009)]

Comments

Copyright 2010 American Physical Society. Available on publisher's site at http://dx.doi.org/10.1103/PhysRevE.81.051706.


Included in

Physics Commons

Share

COinS