EXISTENCE OF A THIRD CRYSTALLINE PHASE IN TBBA

Abstract

Positron annihilation lineshape (S-parameter) measurements and small angle X-ray scattering (SAXS) using synchrotron X-rays on liquid crystalline terepthal-bis-butylaniline (TBBA) are reported at cryogenic temperatures. The crystalline ↔ crystalline transition at 231 K deviates from the first order nature, as evidenced by the observation of a pronounced hysteresis in the layer spacing and the S-Parameter during the heating and cooling cycles. Presence of a possible third crystalline phase at a still lower temperature of 180 K is identified from X-ray diffraction patterns in corroboration with the slope change in layer spacing and electron density variations reflecting on the lineshape parameter.