Axial–biaxial phase transition in discotic liquid crystals, studied by deuterium NMR

Truxenehexaalkanoates (TxHAn) exhibit a variety of discotic mesophases including the sequence ND⇄Drd⇄Dho. The ordering characteristics of these phases were studied by deuterium NMR of deuterated solutes, in particular C6D6. The results indicate that during the phase transition the minor susceptibility axis of the Drd phase transforms into the director axis of the axial phases. It is suggested that in the Drd phase, in alternating columns the mesogen molecules are tilted with respect to the columns axes in opposite directions