Reference : Generation of frustrated liquid crystal phases by mixing an achiral n–smc mesogen wit...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Physics
Generation of frustrated liquid crystal phases by mixing an achiral n–smc mesogen with an antiferroelectric chiral smectic liquid crystal
Lagerwall, Jan mailto [Universität Stuttgart]
Giesselmann, Frank [> >]
Selbmann, Christine [> >]
Rauch, Sebastian [> >]
Heppke, Gerd [> >]
Journal of Chemical Physics
American Institute of Physics
Yes (verified by ORBilu)
New York
[en] X-ray-diffraction ; antiferroelectricity ; binary mixtures
[en] By mixing the achiral liquid crystal HOAB, exhibiting a nematic (N)-smectic-C (SmC) mesophase sequence, with the chiral antiferroelectric liquid crystal (AFLC) (S,S)-M7BBM7, forming the antiferroelectric SmCa phase, at least seven different mesophases have been induced which neither component forms on its own: a twist-grain-boundary (TGB) phase, two or three blue phases, the untilted SmA phase, as well as all three chiral smectic-C-type ``subphases,'' SmCalpha, SmCbeta, and SmCgamma. The nature of the induced phases and the transitions between them were determined by means of optical and electro-optical investigations, dielectric spectroscopy, and differential scanning calorimetry. The induced phases can to a large extent be understood as a result of frustration, TGB at the border between nematic and smectic, the subphases between syn and anticlinic tilted smectic organization. X ray scattering experiments reveal that the smectic layer spacing as well as the degree of smectic order is relatively constant in the whole mixture composition range in which AFLC behavior prevails, whereas both these parameters rapidly decrease as the amount of HOAB is increased to such an extent that no other smectic-C-type phase than SmC/SmC exists. By tailoring the composition we are able to produce liquid crystal mixtures exhibiting unusual phase sequences, e.g., with a direct isotropic-SmCa transition or a temperature range of the SmCbeta subphase of about 50 K. (C) 2005 American Institute of Physics.
Univ Stuttgart, Inst Phys Chem, D-70569 Stuttgart, Germany. Tech Univ Berlin, Dept Chem, Berlin, Germany. Lagerwall, JPF, Univ Stuttgart, Inst Phys Chem, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.

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