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Issue 2, 2013
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Tuning ‘de Vries-like’ properties in siloxane- and carbosilane-terminated smectic liquid crystals

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Abstract

Smectic liquid crystals with ‘de Vries-like’ properties are characterized by a maximum layer contraction of ≤1% upon transition from the non-tilted SmA phase to the tilted SmC phase. To expand the current library of ‘de Vries-like’ liquid crystals, we have developed a rational design strategy based on a concept of frustration between two structural elements, one promoting the formation of a SmA phase (chloro-terminated side-chain) and another promoting the formation of a SmC phase (siloxane-terminated side-chain). In this paper, we show that one can tune this apparent frustration—and further improve de Vries-like properties—by substituting the 2-phenylpyrimidine core in our first-generation siloxane-terminated mesogens with one of three cores known to be stronger SmC-promoting elements: 6-phenylpyridazine, 2-phenylpyridine and 2-phenylthiadiazole. We also address a fundamental design flaw of siloxane-terminated mesogens, i.e., the hydrolytic instability of siloxane oligomers, by substituting the siloxane end-group with a chemically inert carbosilane end-group. As a result of this study, we found a carbosilane-terminated 2-phenylthiadiazole mesogen that forms a SmC phase at room temperature with de Vries-like properties that are comparable to those of bona fide de Vries-like liquid crystals.

Graphical abstract: Tuning ‘de Vries-like’ properties in siloxane- and carbosilane-terminated smectic liquid crystals

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Article information


Submitted
05 Oct 2012
Accepted
25 Oct 2012
First published
25 Oct 2012

J. Mater. Chem. C, 2013,1, 343-350
Article type
Paper

Tuning ‘de Vries-like’ properties in siloxane- and carbosilane-terminated smectic liquid crystals

Q. Song, D. Nonnenmacher, F. Giesselmann and R. P. Lemieux, J. Mater. Chem. C, 2013, 1, 343
DOI: 10.1039/C2TC00338D

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