J. Phys. Colloques
Volume 40, Numéro C3, Avril 19797ème Congrès International sur les Cristaux Liquides
|Page(s)||C3-178 - C3-184|
J. Phys. Colloques 40 (1979) C3-178-C3-184
CHARACTERISATION AND STRUCTURE OF SOME NEW SMECTIC F PHASESA. J. LEADBETTER1, J. P. GAUGHAN1, B. KELLY1, G. W. GRAY2 et J. GOODBY2
1 Department of Chemistry, University of Exeter, Stocker Road, Exeter, EX4 4QD, England
2 Department of Chemistry, University of Hull, Hull, HU6 7RX, England
A number of new compounds of two series have been shown by miscibility studies and optical microscopy to exhibit the hitherto rare smectic F phase. An example of each series has been chosen for detailed X-ray structural investigation : terephthalylidenebis-4-n-pentylaniline (TBPA) and 4-(2'-methyl butylphenyl 4'-n-octyloxybiphenyl-4-carboxylate) (8OSF). The structure of the SF phase has been determined for the first time. Locally it consists of a C centred monoclinic cell with a regular hexagonal packing of the molecules in the layers. The detailed ordering is restricted to about 30 molecular diameters within a layer and to 1 or 2 layers although the gross hexagonal symmetry is preserved throughout the bulk of the sample. The tilt direction of the hexagonal net is different for the two compounds : for TBPA it is towards an edge of the hexagon (as for the SH phase of TBBA) while for 8 OSF it is towards a corner. The SH phases of each compound have essentially the same structure but with longer range order and thetwo different tilt directions are maintained. Preliminary work on the SH phases indicates that they are similar to the SG phase of TBBA but again with two different tilt directions.