All Outputs (36)

Characterization of the Submicrometer Hierarchy Levels in the Twist-Bend Nematic Phase with Nanometric Helices via Photopolymerization. Explanation for the Sign Reversal in the Polar Response (2017)
Journal Article
Panov, V. P., Sreenilayam, S. P., Panarin, Y. P., Vij, J. K., Welch, C. J., & Mehl, G. H. (2017). Characterization of the Submicrometer Hierarchy Levels in the Twist-Bend Nematic Phase with Nanometric Helices via Photopolymerization. Explanation for the Sign Reversal in the Polar Response. Nano Letters, 17(12), 7515-7519. https://doi.org/10.1021/acs.nanolett.7b03441

Photopolymerization of a reactive mesogen mixed with a mesogenic dimer, shown to exhibit the twist-bend nematic phase (NTB), reveals the complex structure of the self-deformation patterns observed in planar cells. The polymerized reactive mesogen ret... Read More about Characterization of the Submicrometer Hierarchy Levels in the Twist-Bend Nematic Phase with Nanometric Helices via Photopolymerization. Explanation for the Sign Reversal in the Polar Response.

Molecular organization in the twist–bend nematic phase by resonant X-ray scattering at the Se K-edge and by SAXS, WAXS and GIXRD (2017)
Journal Article
Stevenson, W. D., Ahmed, Z., Zeng, X. B., Welch, C., Ungar, G., & Mehl, G. H. (2017). Molecular organization in the twist–bend nematic phase by resonant X-ray scattering at the Se K-edge and by SAXS, WAXS and GIXRD. Physical chemistry chemical physics : PCCP, 19(21), 13449-13454. https://doi.org/10.1039/c7cp01404j

© the Owner Societies 2017. Using a magnetically aligned liquid crystal mixture containing a novel Se-labelled dimer and the difluoroterphenyl dimer DTC5C7, the twist-bend nematic phase (N tb ) was studied by the resonant scattering of hard X-rays an... Read More about Molecular organization in the twist–bend nematic phase by resonant X-ray scattering at the Se K-edge and by SAXS, WAXS and GIXRD.

Light scattering study of the “pseudo-layer” compression elastic constant in a twist-bend nematic liquid crystal (2016)
Journal Article
Parsouzi, Z., Pardaev, S. A., Welch, C., Ahmed, Z., Mehl, G. H., Baldwin, A. R., Gleeson, J. T., Lavrentovich, O. D., Allender, D. W., Selinger, J. V., Jákli, A., & Sprunt, S. (2016). Light scattering study of the “pseudo-layer” compression elastic constant in a twist-bend nematic liquid crystal. Physical chemistry chemical physics : PCCP, 18(46), 31645-31652. https://doi.org/10.1039/C6CP06292J

The nematic twist-bend (TB) phase, exhibited by certain achiral thermotropic liquid crystalline (LC) dimers, features a nanometer-scale, heliconical rotation of the average molecular long axis (director) with equally probable left- and right-handed d... Read More about Light scattering study of the “pseudo-layer” compression elastic constant in a twist-bend nematic liquid crystal.

Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers (2016)
Journal Article
Cukrov, G., Mosaddeghian Golestani, Y., Xiang, J., Nastishin, Y. A., Ahmed, Z., Welch, C., Mehl, G. H., & Lavrentovich, O. D. (2017). Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers. Liquid crystals, 44(1), 219-231. https://doi.org/10.1080/02678292.2016.1240248

We report temperature dependencies of material properties such as dielectric anisotropy, birefringence, splay (K₁₁), twist (K₂₂), and bend (K₃₃) elastic constants of the uniaxial nematic (N) phase formed by flexible dimers of DTC5C9 and compare their... Read More about Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers.

Deuteron and proton NMR study of D₂, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases (2016)
Journal Article
Burnell, E. E., Ahmed, Z., Welch, C., Mehl, G. H., & Dong, R. Y. (2016). Deuteron and proton NMR study of D₂, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases. Chemical Physics Letters, 659, 48-54. https://doi.org/10.1016/j.cplett.2016.07.005

The solutes dideuterium, 1,3,5-trichlorobenzene and p-dichlorobenzene (pdcb) are co-dissolved in a 61/39 wt% mixture of CBC9CB/5CB, a bimesogenic liquid crystal with two nematic phases. NMR spectra are collected for each solute. The local electric fi... Read More about Deuteron and proton NMR study of D₂, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases.

Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic-nematic transition (2016)
Journal Article
Sebastián, N., Tamba, M. G., Stannarius, R., de la Fuente, M. R., Salamonczyk, M., Cukrov, G., Gleeson, J., Sprunt, S., Jákli, A., Welch, C., Ahmed, Z., Mehl, G. H., & Eremin, A. (2016). Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic-nematic transition. Physical chemistry chemical physics : PCCP, 18(28), 19299-19308. https://doi.org/10.1039/c6cp03899a

We present structural studies of a dimeric compound composed of a central heptyl spacer linking two mesogens consisiting of terphenyl units at which two adjacent fluoro groups are attached to each central ring. The terminal rings are linked to pentyl... Read More about Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic-nematic transition.

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., Welch, C., Mehl, G. H., Gleeson, J. T., Jakli, A., Lavrentovich, O. D., Allender, D. W., Selinger, J. V., & Sprunt, S. (2016). Fluctuation modes of a twist-bend nematic liquid crystal. Physical Review X, 6(2), 021041-1-021041-16. https://doi.org/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 about Fluctuation modes of a twist-bend nematic liquid crystal.

Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field (2016)
Journal Article
Salili, S. M., Tamba, M. G., Sprunt, S. N., Welch, C., Mehl, G. H., Jákli, A., & Gleeson, J. T. (2016). Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field. Physical review letters, 116(21-27 May), Article 217801. https://doi.org/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 about Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field.

Second harmonic light scattering induced by defects in the twist-bend nematic phase of liquid crystal dimers (2016)
Journal Article
Pardaev, S. A., Shamid, S. M., Tamba, M. G., Welch, C., Mehl, G. H., Gleeson, J. T., Allender, D. W., Selinger, J. V., Ellman, B., Jakli, A., & 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. https://doi.org/10.1039/c6sm00585c

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 about Second harmonic light scattering induced by defects in the twist-bend nematic phase of liquid crystal dimers.

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

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 about The stabilisation of the Nx phase in mixtures.

The design and investigation of the self-assembly of dimers with two nematic phases (2015)
Journal Article
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. https://doi.org/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 about The design and investigation of the self-assembly of dimers with two nematic phases.

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. https://doi.org/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 about NMR study of a bimesogenic liquid crystal with two nematic phases.

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. https://doi.org/10.1080/02678292.2014.984646

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 about Do the short helices exist in the nematic TB phase?.

The design and investigation of nanocomposites containing dimeric nematogens and liquid crystal gold nanoparticles with plasmonic properties showing a nematic-nematic phase transition (Nᵤ-Nₓ/Ntb) (2014)
Journal Article
Tamba, M.-G., Yu, C. H., Tang, B. J., Welch, C., Kohlmeier, A., Schubert, C. P., & Mehl, G. H. (2014). The design and investigation of nanocomposites containing dimeric nematogens and liquid crystal gold nanoparticles with plasmonic properties showing a nematic-nematic phase transition (Nᵤ-Nₓ/Ntb). Materials, 7(5), 3494-3511. https://doi.org/10.3390/ma7053494

The construction of liquid crystal compositions consisting of the dimeric liquid crystal, CB_C9_CB (cyanobiphenyl dimer = 1",9"-bis(4-cyanobiphenyl-4'-yl)nonane), and the range of nematic systems is explored. The materials include a laterally functio... Read More about The design and investigation of nanocomposites containing dimeric nematogens and liquid crystal gold nanoparticles with plasmonic properties showing a nematic-nematic phase transition (Nᵤ-Nₓ/Ntb).

Design, synthesis, and characterization of mesogenic amine-capped nematic gold nanoparticles with surface-enhanced plasmonic resonances (2012)
Journal Article
Yu, C. H., Schubert, C. P. J., Welch, C., Tang, B. J., Tamba, M. G., & Mehl, G. H. (2012). Design, synthesis, and characterization of mesogenic amine-capped nematic gold nanoparticles with surface-enhanced plasmonic resonances. Journal of the American Chemical Society, 134(11), 5076-5079. https://doi.org/10.1021/ja300492d

The use of the liquid-crystalline state to control the assembly of large (>5 nm) gold nanoparticles (NPs) is of considerable interest because of the promise of novel metamaterial properties of such systems. Here we report on a new approach for the pr... Read More about Design, synthesis, and characterization of mesogenic amine-capped nematic gold nanoparticles with surface-enhanced plasmonic resonances.

Reductive Amination-A convenient method for generating diverse, mono-functionalised 5,10,15,20-tetraphenyl porphyrins (2009)
Journal Article
Welch, C., Archibald, S. J., & Boyle, R. (2009). Reductive Amination-A convenient method for generating diverse, mono-functionalised 5,10,15,20-tetraphenyl porphyrins. SYNTHESIS, 2009(4), 551-556. https://doi.org/10.1055/s-0028-1083335

Formylation followed by reductive amination of 5,10,15,20-tetraphenyl porphyrin (TPP) is shown to be a versatile synthetic procedure for monosubstitution of the porphyrin core re-giospecifically at one β-position. A diverse range of substituents can... Read More about Reductive Amination-A convenient method for generating diverse, mono-functionalised 5,10,15,20-tetraphenyl porphyrins.