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Synthesis and characterization of a ...

Mansdorf, Bart Allan.

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Synthesis and characterization of a series of rod-disc combined liquid crystals.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Synthesis and characterization of a series of rod-disc combined liquid crystals./
作者:	Mansdorf, Bart Allan.
面頁冊數:	154 p.
附註:	Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4946.
Contained By:	Dissertation Abstracts International64-10B.
標題:	Chemistry, Organic. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3108216
ISBN:	0496557634

Synthesis and characterization of a series of rod-disc combined liquid crystals.
Mansdorf, Bart Allan.

Synthesis and characterization of a series of rod-disc combined liquid crystals. - 154 p.

Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4946.

Thesis (Ph.D.)--The University of Akron, 2004.

This research was divided into two parts. The objective of the first part was to develop a scheme for synthesizing a series of compounds that contained six cyanobiphenyl mesogens attached to a triphenylene core with (variable length) methylene spacer groups (from 6--12). Seven compounds were synthesized through a four-step process to give the desired product: RDn (R, rod-shaped mesogen; D, discotic mesogen; n, number of methylene spacer groups) with an overall yield of approximately 5%. The purity of each product was confirmed using 1H and 13C NMR, FTIR, MALDI-TOF MS, and elemental analysis.

ISBN: 0496557634Subjects--Topical Terms:

516206
Chemistry, Organic.

Synthesis and characterization of a series of rod-disc combined liquid crystals.
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245 1 0 $a Synthesis and characterization of a series of rod-disc combined liquid crystals.
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500 $a Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4946.
500 $a Adviser: Stephen Z. D. Cheng.
502 $a Thesis (Ph.D.)--The University of Akron, 2004.
520 $a This research was divided into two parts. The objective of the first part was to develop a scheme for synthesizing a series of compounds that contained six cyanobiphenyl mesogens attached to a triphenylene core with (variable length) methylene spacer groups (from 6--12). Seven compounds were synthesized through a four-step process to give the desired product: RDn (R, rod-shaped mesogen; D, discotic mesogen; n, number of methylene spacer groups) with an overall yield of approximately 5%. The purity of each product was confirmed using 1H and 13C NMR, FTIR, MALDI-TOF MS, and elemental analysis.
520 $a The objective of the second part of this research was to determine the structure and phase behavior of these compounds as well as investigate the effects of an electric field on the structure of these materials. Using DSC, the clearing temperatures of the RDn samples increased with a decrease in the spacer length (from Ti = 173°C for RD6 to Ti = 121°C for RD11) while showing an odd-even effect. After studying the thermal transitions in DSC, a more in-depth analysis of the RD10 and RD12 samples was carried out. Using PLM (polarized optical microscope) and WAXD, a nematic phase and two different crystalline phases were identified in RD10 and RD12. In order to investigate the effect of an electric field on RD12, a LC cell was constructed. The cell was filled with the sample and heated to the nematic phase and placed under a PLM. A DC electric field was applied to the cell that resulted in a nearly linear change in birefringence of the sample with an increase of applied voltage up to a critical value of 150V, where the field of view became completely dark. We speculate that the cyanobiphenyl groups "aligned" in the electric field due to the strong dipole moment on the cyano group. We speculate that this molecule behaves like a closing "umbrella" with the cyanobiphenyl groups aligning in the electric field and the discotic cores remaining flat or perpendicular to the field. The result is a 3-dimensionally chiral structure from an achiral material.
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