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From Crystal to Columnar Discotic Liquid Crystal Phases: Phase Structural Characterization of Series of Novel Phenazines Potentially Useful in Organic Electronics

Leng, Siwei
http://rave.ohiolink.edu/etdc/view?acc_num=akron1247614330

Abstract Details

2009, Doctor of Philosophy, University of Akron, Polymer Science.
Four series of potential organic electronic materials have been designed and synthesized to investigate the effects of fused rigid ring size and shape as well as the location, lengths, and chemical structures of their flexible side chain on phase properties. One of these series of conjugated compounds, TQPP-[SCn]4, was synthesized. It was determined that the transition temperatures of this series of compounds can be tuned by modifying the attached alkyl chains. DSC, WAXD, and SAED studies indicated that the condensed state phase transitions of these compounds were all crystal-crystal transitions. To achieve liquid crystalline phases, another of series compounds, TQPP-[t-Bu]2-[OR(B)]4 with an attached bulky tert-butyl group at the 2 and 11 positions have been designed. A columnar liquid crystalline phase (Colr) with C2/m symmetry at high temperature has been identified in these compounds. A high ordered liquid crystalline phase at room temperature has been obtained in TQPP-[t-Bu]2-[OC20H41B]4. By extending the rigid core, TPPQPP-[t-Bu]2-[OR(B)]4 was synthesized and shows a higher isotropization temperature than those with the same substituents in TQPP-[t-Bu-[OR(B)]2. The Colr phase with C2/m symmetry also has been detected at high temperature in TPPQPP-[t-Bu]2-[OC20H41B]4. A unique phase with a crystalline phase within each of the columns while lacking the long-range order among the side chains at room temperature has also been identified. It is the result of a well-adjusted balance between the size of the core and the length and structure of side chains. Thermal behaviors of HDATAN-[OR]6 were complicated when the symmetry of the rigid core changes to three-fold. A crystalline phase only can be formed at elevated temperature during heating or by mechanical shear in compounds with shorter sides chains (R= -C10H21 and -C11H23). Only crystalline phases were identified in the compounds with longer side chains (R= -C14H21 and -C15H23). Based on the experimental results observed, we can conclude that changes in the alkyl tail’s architecture affect the phase behavior more significantly than changes in its length. Tailoring the alkyl tail size, core size, and core shape leads to a promising way to design the discotic columnar liquid crystalline phase.
Stephen Z. D. Cheng, PhD (Advisor)
195 p.
Columnar Discotic Liquid Crystal; Phase Structure; Phenazines; Organic Electronics

Recommended Citations

Citations

  • Leng, S. (2009). From Crystal to Columnar Discotic Liquid Crystal Phases: Phase Structural Characterization of Series of Novel Phenazines Potentially Useful in Organic Electronics [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1247614330

    APA Style (7th edition)

  • Leng, Siwei. From Crystal to Columnar Discotic Liquid Crystal Phases: Phase Structural Characterization of Series of Novel Phenazines Potentially Useful in Organic Electronics. 2009. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1247614330.

    MLA Style (8th edition)

  • Leng, Siwei. "From Crystal to Columnar Discotic Liquid Crystal Phases: Phase Structural Characterization of Series of Novel Phenazines Potentially Useful in Organic Electronics." Doctoral dissertation, University of Akron, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1247614330

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.