Thermotropic Liquid-CrystalIine Behavior of Alkylammonium X-Substituted Benzenesulfonates

Abstract

Five series of smectogenic alkylammonium (C _n H_2n+1NH⁺ ₃) benzenesulfonates were prepared introducing p−chloro, p−hydroxy, o-nitro, m−nitro, and 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 depends significantly upon the alkyl chain length when X = OH and NO₂ but not much when X = Cl and n ⩾ 6. Combining with the results reported earlier, the following group efficiency order in promoting the thermal stability of smectic A phase was made for the octadecylammonium salts: p−OH > p-Cl > p−NO₂ > m−NO₂ > p−CH₃ > H > p−C₂H₃ > o−NO₂.

Key Words:

• Smectic
• alkylammonium salts
• benzenesulfonates
• effects of substituents