Phase Structure and Polymorphism of n-Alkyl Monoesters of Biphenyl-4,4′-dicarboxylic Acid

The phase structure of the n-alkyl monoesters of biphenyl-4,4′-dicarboxylic acid has been investigated using optical microscopy and X-ray diffraction techniques. A polymorphism N, SC' SF and crystal B has been found which is understandable because of the essentially 2-d correlated smectic F phase with only a small interlayer correlation and the extensive 3-d correlation of the smectic B phase. The formation of dimers via H-bridges and an intercalation of the dimers which is active within the first 4 to 5 CH2 groups of the tail groups of the dimers in both ends have been proven by X-ray diffraction.