Thermal Studies on the Phase Transitions ofp-n-Octadecyloxy Benzoic Acid (Part I)

Thermal properties of p-n-octadecyloxybenzoic acid were investigated and the effects of the long paraffinic chain attached to the benzoic acid on the molecular motion in the mesophase are discussed. It was found that p-n-octadecyloxybenzoic acid had three crystalline forms; Crystal-I, Crystal-II and Crystal-III. Crystal-I is stable and Crystal-II and -III are metastable. It was concluded that the paraffinic chain in the Crystal-I. It is suggested that p-n-alkoxybenzoic acids in general, has physical properties of both liquid and plastic crystals.