Reference : On the balance between syn- and anticlinicity in smectic phases formed by achiral hoc...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
http://hdl.handle.net/10993/20515
On the balance between syn- and anticlinicity in smectic phases formed by achiral hockey-stick mesogens with and without chiral dopants
English
Enz, Eva [> >]
Findeisen-Tandel, Sonja [> >]
Dabrowski, Roman [> >]
Giesselmann, Frank [> >]
Weissflog, Wolfgang [> >]
Baumeister, Ute [> >]
Lagerwall, Jan mailto [Martin-Luther-Universität Halle-Wittenberg]
2009
Journal of Materials Chemistry
Royal Society of Chemistry
19
19
2950-2957
Yes (verified by ORBilu)
International
0959-9428
1364-5501
Cambridge
United Kingdom
[en] FERROELECTRIC LIQUID-CRYSTALS; SPONTANEOUS POLARIZATION; SHAPED   COMPOUNDS; FIELD; MESOPHASES; MOLECULES
[en] A series of achiral hockey-stick-shaped mesogens forming tilted smectic liquid crystal phases of synclinic SmC- as well as anticlinic SmCa-type was prepared and characterized. While all homologues exhibit both phases, the balance shifts from anticlinic to synclinic order upon elongation of the terminal chain at the meta-position, defining the hockey-stick shape. The elongation also leads to an increased kinetic hindrance of the transition between syn- and anticlinic phases and a decreased transition enthalpy. These observations indicate that a well-defined kink (short meta-substituted chain) promotes the anticlinic structure while a higher flexibility between kinked and rod-shape (long meta-substituted chain) promotes synclinic order. An intermediate chain-length homologue was selected as host material for doping with syn- and anticlinic rod-shaped chiral dopants, respectively, at varying concentrations. Opposite of what might be expected the balance between syn- and anticlinic order was not simply dictated by the choice of dopant. Instead, both types of tilting order prevailed with roughly the same strength as in the achiral host regardless of which chiral material was added, up to concentrations well beyond normal doping conditions. Thus, at least with hockey-stick-shaped achiral hosts, syn- as well as anticlinic chiral compounds can be used effectively as chiral dopants without necessarily having an important impact on the clinicity of the resulting mixture. The hockey-stick design concept should be useful in producing achiral anticlinic-forming mesogens for low-polarization, long-pitch antiferroelectric liquid crystal mixtures. Finally, we point out that a mixture study like the one carried out here yields a conclusive means of establishing the clinicity of achiral tilted smectics, an endeavour that can sometimes be far from trivial.
Researchers
http://hdl.handle.net/10993/20515
10.1039/b820717h
[Enz, Eva; Findeisen-Tandel, Sonja; Weissflog, Wolfgang; Baumeister, Ute; Lagerwall, Jan] Univ Halle Wittenberg, Inst Chem Phys Chem, D-06108 Halle, Germany.   [Enz, Eva; Giesselmann, Frank; Lagerwall, Jan] Univ Stuttgart, Inst Phys Chem, D-70569 Stuttgart, Germany.   [Dabrowski, Roman] Mil Univ Technol, PL-00908 Warsaw, Poland.   [Findeisen-Tandel, Sonja] Univ Cambridge, Dept Engn, Ctr Mol Mat Photon Elect, Cambridge CB2 1TN, England. Lagerwall, J, Univ Halle Wittenberg, Inst Chem Phys Chem, Muehlpforte   1, D-06108 Halle, Germany.

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