Further X-Ray Studies of Mesophase Structure of Hexakis(Alkylsulfono)Benzene (HASBn) and Tribenzocyclononene (ll-n) Homologues

Abstract

Mesophase forming compounds of hexakis(alkylsulfono)benzene compounds (HASBn) are found for n = 7 to 15 carbons per sidechain. We compare X-ray studies for n = 14 with previous results for n = 13. The diffraction patterns indicate a more disordered structure for n = 14, even in the room temperature crystalline phase. The mesophase diffraction pattern is consistent with hexagonal packing of disordered discotic columns, with average lattice repeat a = 29.3 Å. The (10), (11), and (20) reflections are observed with the last one being barely detectible. A fourth broad scattering peak centered about a spacing of about 5.0 Å is attributed to the spacing between molecules within the columns. These numbers are slightly larger than the corresponding numbers for n = 13, as should be expected.

Four different homologous series of tribenzocyclononene compounds have been studied. Compounds in series II having 8 to 15 carbon atoms per sidechain exhibit mesomorphism, with structures based on columns of pyramidic or “bowlic” molecules. We compare results obtained from compound II-15 (15 carbon atoms per sidechain) with results obtained from other compounds in this series. The diffraction pattern indicates considerably more disorder for II-15 than for II-13 at all temperatures.

Out of five observed features in the hexagonal mesophase, 4 diffraction lines are most simply indexed in terms of a lattice parameter of 59.7 Å. The (11), (20), (22) and (40) reflections are observed but not the (10) reflection.

Key Words:

• structure of mesophase
• x-ray diffraction