Thermal Behavior of Crystalline Polymorphs of nOCB

Abstract

Crystalline polymorphs of nOCB were investigated by using differential scanning calorimetry(DSC). The square-plate crystal form, which is composed of distinct smectic-like bilayer structure with infinite network of the proximity of CN groups, appears in common for each of all the homologues (n≥-7). It is in a metastable state for n=7, 8. On the other hand, it is the most stable state at room temperature and transforms to a higher-temperature crystalline phase, which is found in commercially available specimen as a supercooled phase, before it transforms to the smectic A for n≥-9.