Bimodal form distribution from modelling biaxial lyotropic liquid crystal solutions through a polydisperse Maier–Saupe model

ABSTRACT

Biaxial nematic phases have been the subject of a long list of studies. In particular, they were found for a few lyotropic micellar solutions. There is a debate in the literature on whether the micellar aggregates should be biaxial, or if biaxiality could be the result of perpendicular alignment of uniaxial particles of cylinder-like and disc-like geometry in a mixture. Based on recent studies on the phase stability of such mixtures, we have investigated a polydisperse distribution of uniaxial particles interacting through a Maier–Saupe potential. Our calculations were developed for a general distribution of micellar anisometries. The distribution was obtained from the fitting of our results to the experimental data of Yu and Saupe’s well-known 1980 paper, near the Landau point, yielding a bimodal distribution, with the presence of two quadrupoles referred to objects of opposite symmetry, that is to prolate and oblate micelles. This result lends support to the rationalization of the biaxial phase for lyotropic systems in terms of a polydisperse mixture of rod-like and disc-like micelles.

GRAPHICAL ABSTRACT

KEYWORDS:

• Maier–Saupe model
• biaxial lyotropic nematic
• Landau–de Gennes expansion
• polydisperse distribution

Acknowledgements

One of the authors acknowledges a fellowship of Fapesp, and the hospitality of the Instituto de Física da USP, São Paulo (IFUSP). We specially thank Prof. S. R. A. Salinas, from IFUSP, for discussions and helpful revision of the text. We also thank professors Domingos H.U. Marchetti and Leandro R. S. Barbosa, from IFUSP, and Willian S. Barros, from the Instituto de Física e Matemática da UFPel.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Fapesp, and the hospitality of the Instituto de Física da USP, São Paulo (IFUSP).