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The induction of the Ntb phase in mixtures (2018)
Journal Article
Ramou, E., Welch, C., Hussey, J., Ahmed, Z., Karahaliou, P. K., & Mehl, G. H. (2018). The induction of the Ntb phase in mixtures. Liquid crystals, 45(13-15), 1929-1935. doi:10.1080/02678292.2018.1524523

We report the induction of the Ntb phase over a wide temperature and concentration range in a binary system. This was achieved by addition of a flexible dopant without LC properties to a flexible dimer exhibiting only a nematic LC phase. The Ntb phas... Read More

Supramolecular organization of liquid-crystal dimers-bis-cyanobiphenyl alkanes on HOPG by scanning tunneling microscopy (2018)
Journal Article
Krzyzewska, K., Jaroch, T., Maranda-Niedbała, A., Pociecha, D., Górecka, E., Ahmed, Z., …Nowakowski, R. (2018). Supramolecular organization of liquid-crystal dimers-bis-cyanobiphenyl alkanes on HOPG by scanning tunneling microscopy. Nanoscale, 10(34), 16201-16210. doi:10.1039/c8nr02069h

2D supramolecular organization of a series of six cyanobiphenyl bimesogens deposited on highly oriented pyrolytic graphite (HOPG) is studied by scanning tunneling microscopy (STM). The adsorbates are 1,ω-bis(4-cyanobiphenyl-4’-yl)alkanes (CBnCB) with... Read More

Characterization of large tilt-angle flexoelectro-optic switching in chiral nematic liquid crystal devices (2018)
Journal Article
Wang, X., Fells, J. A. J., Welch, C., Tamba, M., Mehl, G. H., Morris, S. M., & Elston, S. J. (2018). Characterization of large tilt-angle flexoelectro-optic switching in chiral nematic liquid crystal devices. Liquid crystals, 1-7. doi:10.1080/02678292.2018.1502822

The “flexoelastic ratio”, which is the ratio of the effective flexoelectric coefficient to the elastic coefficients, is commonly used to characterize the electro-optic behavior of chiral nematic liquid crystal (LC) devices that exhibit flexoelectro-o... Read More

Fluctuation modes of a twist-bend nematic liquid crystal (2016)
Journal Article
Parsouzi, Z., Shamid, S. M., Borshch, V., Challa, P. K., Baldwin, A. R., Tamba, M. G., …Sprunt, S. (2016). Fluctuation modes of a twist-bend nematic liquid crystal. Physical Review X, 6(2), 021041-1-021041-16. doi:10.1103/PhysRevX.6.021041

We report a dynamic light-scattering study of the fluctuation modes in a thermotropic liquid crystalline mixture of monomer and dimer compounds that exhibits the twist-bend nematic (NTB) phase. The results reveal a spectrum of overdamped fluctuations... Read More

Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field (2016)
Journal Article
(2016). Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field. Physical review letters, 116(21-27 May), doi:10.1103/PhysRevLett.116.217801

We have determined the nematic-isotropic transition temperature as a function of applied magnetic field in three different thermotropic liquid crystalline dimers. These molecules are comprised of two rigid calamitic moieties joined end to end by flex... Read More

Second harmonic light scattering induced by defects in the twist-bend nematic phase of liquid crystal dimers (2016)
Journal Article
Shamid, S. M., Pardaev, S. A., Tamba, M. G., Mehl, G. H., Gleeson, J. T., Allender, D. W., …Sprunt, S. (2016). Second harmonic light scattering induced by defects in the twist-bend nematic phase of liquid crystal dimers. Soft matter, 12(19), (4472-4482). doi:10.1039/c6sm00585c. ISSN 1744-683X

The nematic twist-bend (NTB) phase, exhibited by certain thermotropic liquid crystalline (LC) dimers, represents a new orientationally ordered mesophase -- the first distinct nematic variant discovered in many years. The NTB phase is distinguished by... Read More

The stabilisation of the Nx phase in mixtures (2016)
Journal Article
Ahmed, Z., Mehl, G. H., Welch, C., Karahaliou, P. K., & Ramou, E. (2016). The stabilisation of the Nx phase in mixtures. Soft matter, 12(3), (888-899). doi:10.1039/c5sm01961c. ISSN 1744-683X

The phase behaviour of mixtures between two symmetric dimers, CBC9CB and the ether-linked analogue CBOC9OCB was investigated by Polarizing Optical Microscopy (POM), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) studies. The dime... Read More

The design and investigation of the self-assembly of dimers with two nematic phases (2015)
Journal Article
H. Mehl, G. H., Ahmed, Z., Welch, C., & Mehl, G. H. (2015). The design and investigation of the self-assembly of dimers with two nematic phases. RSC advances, 5(113), 93513-93521. doi:10.1039/c5ra18118f

A series of non-symmetric dimers were synthesised containing either cyanobiphenyl or difluoroterphenyl moieties on one side and a range of long, short, bent, polar or apolar mesogens on the other side of the molecules. The dielectric anisotropy of th... Read More

NMR study of a bimesogenic liquid crystal with two nematic phases (2015)
Journal Article
Burnell, E. E., Dong, R. Y., Kohlmeier, A., Tamba, M. G., Welch, C., & Mehl, G. H. (2015). NMR study of a bimesogenic liquid crystal with two nematic phases. Molecular crystals and liquid crystals, 610(1), 100-107. doi:10.1080/15421406.2015.1025211

Recent interest in bimesogenic liquid crystals showing two nematic phases has led us to investigate the nematic mean-field interactions in these nematic phases by using rigid solutes as probes. The nematic potential that is modelled by two independen... Read More

Do the short helices exist in the nematic TB phase? (2015)
Journal Article
Górecka, E., Salamończyk, M., Zep, A., Pociecha, D., Welch, C., Ahmed, Z., & Mehl, G. H. (2015). Do the short helices exist in the nematic TB phase?. Liquid crystals, 42(1), (1-7). doi:10.1080/02678292.2014.984646. ISSN 0267-8292

Dimeric compounds forming twist-bend nematic, Ntb, phase show unusual optical textures related to the formation of arrays of focal conic defects (FCDs). Some of the focal conics exhibit submicron internal structure with 8 nm periodicity, which is ver... Read More