Deuterium NMR Investigation of a Discotic Mesogen Based on

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J. Phys. Chem. 1995,99, 6661-6669

Deuterium NMR Investigation of a Discotic Mesogen Based on Hexasubstituted Truxene D. SandstriSm,*J M. Nygren,' H. Zimmermann? and A. Maliniakt Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, S-10691 Stockholm, Sweden, Division of Inorganic Chemistry, Arrhenius Laboratory, Stockholm University, S-10691 Stockholm, Sweden, and Max-Planck-Institut f i r Medizinische Forschung, AG Molekiilkristalle, 69028 Heidelberg 1, Gemuzny Received: November 23, 1994; In Final Form: January 10, I995@

We report a 2H nuclear magnetic resonance (NMR) investigation of 2,3,7,8,12,13-hexakis(octadecanoyloxy)truxene (TxHA17) specifically labeled in the a-position of the alkyl chain. Results from these measurements, together with polarizing microscopy, show that the substance is in a crystalline state up to 90 "C. At this temperature the compound melts and a uniaxial discotic mesophase appears. The liquid crystalline phase persists until the clearing point at 191 "C. The differential scanning calorimetry thermograms confirmed these transitions but exhibited additional peaks below 90 "C. The phase behavior at low temperatures (