Crystallization and Melting of Metastable Solid Crystalline Phases of EBBA

Abstract

The solid crystalline (SC) polymorphism of nematogenic compounds has not been thoroughly investigated. Three SC modifications have been found for the most studied nematogencies, PAA and MBBA. ^1,2 Calorimetric data are known ^2,3 only for one metastable MBBA phase. Raman spectra⁴ of EBBA identifies four SC forms which transform from one form to others only in one direction. Solid crstalline phaes are numbered in Gigure 1 according to the sequence of monotropic transformations. These transformations are represented as SCI SCII SCIII SCIV, where SC IV is a stable form obtained normally by crystallization from alcohol solution.