© 2017 American Physical Society. This is an author produced version of a paper published in Physical Review E. Uploaded in accordance with the publisher's self-archiving policy.eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. A detailed investigation of the thermal and dielectric properties of a series of binary mixtures exhibiting the nematic (N) and twist-bend nematic (NTB) liquid crystal phases is presented. The mixtures consist of an achiral, dimeric liquid crystal CB7CB, which forms the nematic and twist-bend nematic phases, and a calamitic liquid crystal 5CB, which shows the nematic phase. As the concentration of the calamitic liquid crystal is increased, the transition temperatures decrease linearly, and the width of the nematic phase increases. The enthalpies of phase transitions obtained from DSC measurements show that on increasing the concentration of 5CB in the binary mixtures, the enthalpy associated with the N to NTB phase transitions reduces considerably compared to a clear first order N-NTB transition in pure CB7CB. The real and imaginary parts of the dielectric permittivity are measured as a function of frequency from 100 Hz to 2 MHz in the nematic and twist-bend nematic phases in planar and homeotropic devices. A significant decrease in the average dielectric permittivity as a function of temperature for mixtures forming the NTB phase is observed. Measurements of the imaginary part of the dielectric permittivity show a relaxation peak in the measured frequency window for all of the mixtures exhibiting the NTB phase. The activation energy associated with this relaxation process is calculated and is shown to remain constant irrespective of the composition of the mixtures.2

All chemicals were, unless stated otherwise, provided by the supplier and used without further purification. Dry solvents were dried by conventional laboratory methods. The eluents for chromatography petroleum ether (low-boiling) and ethyl acetate were distilled prior to use.For thinlayer chromatography silica gel 60 F254 glass plates with a layer thickness of 0.25 mm on aluminium (pore size 60 Å) from the company Merck were used. Column chromatography was performed using silica gel with a particle diameter of 40 -60 µm from the company Fluka.1 H NMR spectra were measured using the Bruker Avance 300 and Bruker Avance 500 spectrometers at 300 MHz and 500 MHz, respectively and 13 C-NMR spectra at 75 MHz and 126 MHz, respectively. Deuterated chloroform (CDCl3) and deuterated dimethyl sulfoxide (DMSO-d6) were used as solvents. The chemical shift δ in ppm (parts per million) refers to the standard tetramethylsilane. The numbering of atoms can be different from the IUPAC nomenclature in order to ensure better comparison of various compounds. In order to assign the signals of the 1 H and 13 C NMR spectra, COSY, HSQC and HMBC measurements were carried out.

This is a repository copy of Metastable room-temperature twist-bend nematic phases via photopolymerization.

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