Proton NMR relaxation study of molecular dynamics of chromonic liquid crystal Edicol Sunset Yellow

Abstract

Proton nuclear magnetic resonance (¹H NMR) relaxometry, over about five decades in Larmor frequency, and pulsed field gradient NMR were used to study the molecular dynamics in the chromonic nematic and isotropic phases of stacked molecules of the binary mixture composed by Edicol Sunset Yellow (ESY) and deuterated water. Our results evidence that in both phases collective motions are responsible for the spin-lattice relaxation dispersion in the Larmor frequency range below 1 MHz. In the nematic phase, the collective motion are attributed to columnar undulations within the stacked molecules, while, in the isotropic phase, the results are explained by local order fluctuations due to the formation of the stacks. The high frequency dispersion was explained by individual molecular motions like rotations around and perpendicular to the stack axis, and also self-diffusion.

Keywords:

• NMR
• relaxation
• chromonics
• dynamics
• sunset yellow

Acknowledgements

We thank Laura Saavedra and Rui Malhõ for the Edicol Sunset Yellow purification.

Funding

Funding of this work was provided by Fundação para a Ciência e a Tecnologia (FCT), Project PEst-C/CTM/LA0025/2022 (Strategic Project – LA 25–2001/2012) and Portuguese Nuclear Magnetic Resonance Network (PRNMR).

Supplemental data

Supplemental data for this article can be accessed here.