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Proton and Deuterium NMR study of the CBC9CB Dimer System

Carvalho, José; Cruz, Carlos; Figueirinhas, João L.; Tamba, Maria-Gabriela; Kohlmeier, Alexandra; Mehl, G. H.

Authors

José Carvalho

Carlos Cruz

João L. Figueirinhas

Maria-Gabriela Tamba

Alexandra Kohlmeier



Contributors

Abstract

Copyright © 2019 American Chemical Society. Using proton and deuterium NMR spectroscopy, this work provides a description of the molecular orientational order of the mesogenic groups in both the N tb and the classical nematic phase (N) of the liquid crystal dimer CB-C9-CB. The proton NMR data were collected at high field (7 T) with the nematic domains aligned by the field. Deuterium NMR data obtained from aligned samples at 11.7 T, published by Hoffmann, A. et al. Soft Matter 2015, 11, 850, were also considered in this study. Using the first-order perturbation theory, we carried out detailed simulations of the proton spectra from the terminal mesogenic groups along with the quadrupolar splittings from the carbon-deuterium bonds in the first chain positions, which allow for the determination of the Saupe order tensor for the mesogenic groups. We show that the main mechanism that induces the change of the 1 H NMR spectrum and the quadrupolar splittings at the N-N tb phase transition is the change of the orientation of the most ordered molecular frame (eigenframe of the Saupe tensor), along with the onset of the molecular biaxiality parameter, D. This orientation change is associated with the achiral symmetry breaking at the N-N tb phase transition.

Citation

Carvalho, J., Cruz, C., Figueirinhas, J. L., Tamba, M., Kohlmeier, A., & Mehl, G. H. (2019). Proton and Deuterium NMR study of the CBC9CB Dimer System. Journal of Physical Chemistry B, 123(6), 1442-1451. https://doi.org/10.1021/acs.jpcb.8b11526

Journal Article Type Article
Acceptance Date Jan 10, 2019
Online Publication Date Jan 16, 2019
Publication Date Feb 14, 2019
Deposit Date Jan 28, 2019
Publicly Available Date Oct 27, 2022
Journal Journal of Physical Chemistry B
Print ISSN 1520-6106
Electronic ISSN 1520-5207
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 123
Issue 6
Pages 1442-1451
DOI https://doi.org/10.1021/acs.jpcb.8b11526
Keywords Physical and Theoretical Chemistry; Materials Chemistry; Surfaces, Coatings and Films
Public URL https://hull-repository.worktribe.com/output/1244009
Publisher URL https://pubs.acs.org/doi/10.1021/acs.jpcb.8b11526

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Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in
Journal of Physical Chemistry B, copyright © American Chemical Society after peer review and technical editing by the publisher.
To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acs.jpcb.8b11526







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