posted on 2017-08-22, 00:00authored byAdrian Gainar, Mei-Chun Tzeng, Benoît Heinrich, Bertrand Donnio, Duncan W. Bruce
The
synthesis and liquid crystal properties are reported for tri- and
tetra-catenar mesogens in which both hydrocarbon and semiperfluorocarbon
chains have been incorporated. In the tricatenar mesogens, the lamellar
spacing in the smectic C phase of the all-hydrocarbon mesogen almost
doubles when the isolated hydrocarbon chain is replaced by a semiperfluorinated
chain on account of the localized segregation in different sublayers
between the two chain types. In the tetracatenar materials, the replacement
of at least one hydrocarbon chain by semiperfluorocarbon chains is
sufficient to promote columnar phase formation, but when the molecule
has two hydrocarbon chains at one end and two semiperfluorocarbon
chains at the other, the requirement for localized phase segregation
leads to the formation of a rectangular phase with very large lattice
parameters. The juxtaposition of terminal chains of different nature
within the same molecular structure thus leads to a reduction in mesophase
symmetry and the emergence of more complex supramolecular organization.