THE MESOMORPHIC BEHAVIOR OF CYANOPROPYLALKYLDIMETHYLAMMONIUM BROMIDES

A homologous series of N-cyanopropyl-N-alkyl-N,N-dimethylammonium brom ides was synthesized and characterized. Its thermotropic liquid crysta lline behaviour was studied by differential scanning calorimetry, pola rizing optical microscopy, dilatometry, and X-ray diffraction. A smect ic A mesophase was thus identified. The smectic layers were found to b e formed of two ionic planes alternately separated by sub-layers of di sordered alkyl chains and cyanopropyl groups. The smectic structure wa s compared with that of the crystal at room temperature and also that of the smectic T structure of the N,N-dialkyl-N,N-dimethylammonium bro mides already described in the literature.