Investigation of the structure of polymorphous modifications of fluoroalkylcyclohexanecarboxylic acids by infrared spectroscopy methods

The results of investigation of polymorphism and mesomorphic states of fluorinated derivatives of alkylcyclohexanecarboxylic acids nFACHCA and new results for n=4, 7 are discussed. The methods of vibrational spectroscopy have been used. The samples were investgiated in the 290-500 K temperature range. The spectra were recorded in the range of 400-4000 cm-1. The frequencies of normal modes and IR band intensities are calculated for conformers of H-bonded complexes with varioius orientations of fluoroalkyl radical and carboxylic group relative to the rest of the molecular compelx. The polymorphism of the nFACHCA is conformational. The influence of H-bonds on dynamics of H-bonded complex, polymorphic crystalline modification and mesophase formaiton was determined. The transitions solid crystal-liquid crystal-isotropic liquid and soution are accompanied by H-bond system reconstruction: the dimers, associates, chain associates and monomers appear.