Skip to main content

Probing molecular ordering in the nematic phases of para-linked bimesogen dimers through NMR studies of flexible prochiral solutes

Heist, Leah M.; Samulski, Edward T.; Welch, Chris; Ahmed, Ziauddin; Mehl, Georg H.; Vanakaras, Alexandros G.; Photinos, Demetri J.

Authors

Leah M. Heist

Edward T. Samulski

Chris Welch

Ziauddin Ahmed

Alexandros G. Vanakaras

Demetri J. Photinos



Contributors

Chris Welch
Researcher

Leah Hirst
Researcher

Edward Samulski
Researcher

Abstract

The quadrupolar splittings of perdeuteriated n-decane dissolved in nematic phases formed by mesogenic dimers of the CBnCB series, for n = 7,9,10,11, are measured throughout the entire temperature range of these phases. These results are reported together with related measurements using the common nematic phase of 5CB as a solvent for n-decane. The data obtained from the 13C spectra of the cyanobiphenyl mesogenic units of the monomeric and dimeric solvent molecules yield the order parameter of those units. The information obtained from this set of experiments is used to elucidate the structure of the low temperature (NX) and the high temperature (N) nematic phases of CBnCB dimers with n = 7,9,11. The polar twisted nematic (NPT) model is found to provide a consistent description not only of our experimental results but also of NMR measurements previously reported in the literature for these phases. These findings suggest that the high temperature nematic (N) is not a common, locally uniaxial and apolar nematic, but rather a nematic phase consisting of NPT clusters. The twist-bend (NTB) model, often identified with the NX phase, is shown to be inadequate to account even qualitatively for crucial features of the experimental findings.

NMR studies of perduteriated n-decane dissolved in mesogenic dimers of the CBnCB series elucidate the structure of the low and high temperature nematic phases of the odd-n dimers.

Journal Article Type Article
Journal Liquid Crystals
Print ISSN 0267-8292
Electronic ISSN 1366-5855
Publisher Taylor & Francis
Peer Reviewed Peer Reviewed
Pages 1-16
APA6 Citation Heist, L. M., Samulski, E. T., Welch, C., Ahmed, Z., Mehl, G. H., Vanakaras, A. G., & Photinos, D. J. (in press). Probing molecular ordering in the nematic phases of para-linked bimesogen dimers through NMR studies of flexible prochiral solutes. Liquid crystals, 1-16. https://doi.org/10.1080/02678292.2019.1711214
DOI https://doi.org/10.1080/02678292.2019.1711214
Keywords General Materials Science; General Chemistry; Condensed Matter Physics; Nenatic-nematic phase transitions; NMR; potential of mean torque; symmetric dimers; prochiral solutes
Additional Information Peer Review Statement: The publishing and review policy for this title is described in its Aims & Scope.; Aim & Scope: http://www.tandfonline....ope&journalCode=tlct20; Published: 2020-01-28
;