THERMOTROPIC LIQUID-CRYSTALLINE BEHAVIOR OF ALKYLAMMONIUM X-SUBSTITUTED BENZENESULFONATES

Five series of smectogenic alkylammonium (CnH2n+1NH3+) benzenesulfonat es were prepared introducing p-chloro, p-hydroxy, o-nitro, m-nitro, an d p-nitro substituents to the aromatic nucleus, respectively. All the butyl to octadecylammonium salts exhibit a smectic A phase when X= Cl, whereas only the cation carrying a pentadecyl or a longer alkyl group forms a mesogenic salt when X = OH and NO2. The clearing point depend s significantly upon the alkyl chain length when X = OH and NO2 but no t much when X = Cl and n greater than or equal to 6. Combining with th e results reported earlier, the following group efficiency order in pr omoting the thermal stability of smectic A phase was made for the octa decylammonium salts: p-OH > p-Cl > p-NO2 > m-NO2 > p-CH3 > H > p-C2H5 > o-NO2.