J. Kawamata et al., THERMOTROPIC LIQUID-CRYSTALLINE BEHAVIOR OF ALKYLAMMONIUM X-SUBSTITUTED BENZENESULFONATES, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 257, 1994, pp. 27-33
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.