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Elastic effects in flexible dimeric and elastomer nematics

Babakhanova, Greta
http://orcid.org/0000-0002-5027-5673
http://rave.ohiolink.edu/etdc/view?acc_num=kent155145733547706

Abstract Details

2019, PHD, Kent State University, College of Arts and Sciences / Chemical Physics.
In this dissertation, we explore how the molecular structure of nematic liquid crystals influences their elastic behavior. In the first part, we study the structure-property relationship of flexible low-molecular weight liquid crystal dimers. These dimers were recently demonstrated to form a new liquid crystalline phase, the so-called twist-bend nematic. We report temperature dependencies of material properties such as dielectric anisotropy, birefringence, splay, K1, twist, K2, and bend, K3, elastic constants in the uniaxial nematic phase of these materials and compare these properties to the properties of conventional rod-like nematics. Our studies demonstrate striking differences between flexible dimers and rod-like mesogens. In the case of dimers, the temperature dependent birefringence and bend elastic constant show a non-monotonous behavior on approaching the nematic-to-twist-bend nematic phase transition. Additionally, the conventional relationship of rod-like mesogens follows the trend K3>K1>K2, whereas, in all the studied dimeric compounds we observe a very different trend with K1>K2> K3. The second part of the dissertation addresses stimuli-responsive nematic elastomer coatings formed by polymerized mesogens. The molecular orientation of the liquid crystal elastomers is coupled to rubber-like elasticity. The orientational order defines their mechanical response to external stimuli such as temperature or light. We demonstrate a dynamic thermal control of surface topography of the elastomers prepared as coating with patterned in-plane molecular orientation. Upon heating, the inscribed director pattern determines whether the initially flat coating develops elevations, depressions or in-plane deformations. We explain this deterministic relationship between the in-plane orientations and out-of-plane variations of coatings’ profile by the activation forces concept. We employ the light-activated elastomer coatings with 2D inscribed orientational order as a tool for controlled placement of microparticles at the water-liquid crystal elastomer interface.
Oleg Lavrentovich (Advisor)
Antal Jákli (Committee Member)
Samuel Sprunt (Committee Member)
Min-Ho Kim (Committee Member)
128 p.
Chemistry; Materials Science; Physics
liquid crystals, twist-bend nematic phase, elastic constants, stimuli-responsive elastomers, biocompatible surfaces

Recommended Citations

Citations

  • Babakhanova, G. (2019). Elastic effects in flexible dimeric and elastomer nematics [Doctoral dissertation, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent155145733547706

    APA Style (7th edition)

  • Babakhanova, Greta. Elastic effects in flexible dimeric and elastomer nematics. 2019. Kent State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent155145733547706.

    MLA Style (8th edition)

  • Babakhanova, Greta. "Elastic effects in flexible dimeric and elastomer nematics." Doctoral dissertation, Kent State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent155145733547706

    Chicago Manual of Style (17th edition)

kent155145733547706
385
© 2019, some rights reserved.Creative Commons License Elastic effects in flexible dimeric and elastomer nematics by Greta Babakhanova 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.