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Dynamic and Magneto-optic Properties of Bent-core Liquid Crystals

Salili, Seyyed Muhammad
http://rave.ohiolink.edu/etdc/view?acc_num=kent1479906074401674

Abstract Details

2016, PHD, Kent State University, College of Arts and Sciences / Chemical Physics.
In this work, we describe dynamic behavior of free-standing bent-core liquid crystal filaments under dilative and axial compressive stresses in the B7 phase. We found that such filaments demonstrate very complex structures depending on the filament’s temperature relative to the isotropic phase, initial filament thickness, and velocity at which the filament is pulled or compressed. We also present our experimental methods, results and analysis of the rupture and recoil properties of several bent-core liquid crystal filaments, anticipating that they may serve as a model system for complex biological fibers. After that, we systematically describe rheological measurements for dimeric liquid crystal compounds. We studied the shear-induced alignment properties, measured the viscoelastic properties as a function of temperature, shear rate, stress and frequency, and compared the results with the rheological properties of conventional chiral nematic and smectic phases. Then we present results of chiral nematic liquid crystals composed of flexible dimer molecules subject to large DC magnetic fields between 0 and 31T. We observe that these fields lead to selective reflection of light depending on temperature and magnetic field. The band of reflected wavelengths can be tuned from ultraviolet to beyond the IR-C band. A similar effect induced by electric fields has been presented previously, and was explained by a field-induced oblique-heliconical director deformation in accordance with early theoretical predictions. Finally, we report an unprecedented magnetic field-induced shifts of the isotropic-nematic phase transition temperature observed in liquid crystal dimers where two rigid linear mesogens are linked by flexible chains of either even- or odd-numbered hydrocarbon groups. This effect is explained in terms of quenching of the thermal fluctuations and decrease of the average bend angle of molecules in the odd-numbered dimers.
Antal Jakli, PhD (Advisor)
John West, PhD (Committee Member)
Samuel Sprunt, PhD (Committee Member)
138 p.
Chemistry; Physics
liquid crystal; bent-core; rheology of liquid crystal; cholesterics; twist-bend nematic; liquid crystal dimer; tunable selective reflection; liquid crystal fiber; liquid crystal filament; birefringence; magneto-optic

Recommended Citations

Citations

  • Salili, S. M. (2016). Dynamic and Magneto-optic Properties of Bent-core Liquid Crystals [Doctoral dissertation, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1479906074401674

    APA Style (7th edition)

  • Salili, Seyyed Muhammad. Dynamic and Magneto-optic Properties of Bent-core Liquid Crystals. 2016. Kent State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1479906074401674.

    MLA Style (8th edition)

  • Salili, Seyyed Muhammad. "Dynamic and Magneto-optic Properties of Bent-core Liquid Crystals." Doctoral dissertation, Kent State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1479906074401674

    Chicago Manual of Style (17th edition)

kent1479906074401674
660
© 2016, some rights reserved.Creative Commons License Dynamic and Magneto-optic Properties of Bent-core Liquid Crystals by Seyyed Muhammad Salili is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Kent State University and OhioLINK.