Mesomorphic behaviour of N-(n-alkyl) pyridinium hydrogensulfates

Ionic Liquid Crystals

“…In a structural model for N -( n -hexadecyl)-4-cyanopyridinium iodide, the authors propose a pairing of the iodide ions. The N -alkylpyridinium hydrogen sulfates are thermotropic liquid crystals, but the mesophase behavior has not been investigated in detail yet . Interestingly, these compounds form lyotropic mesophases in concentrated sulfuric acid, and the phase sequence as a function of the concentration of the pyridinium salt is similar to the sequence found for cationic surfactants in aqueous solution.…”

Thermotropic Phase Behavior of Cationic Gemini Surfactants and Their Equicharge Mixtures with Sodium Dodecyl Sulfate

“…However, the measured enthalpies were not analyzed in detail for crystal-to-crystal transition, particularly as a function of the chain length, because of a complex polymorphism in the solid state difficult to control, and no clearing temperature from smectic phase to isotropic liquid was detected. For long-chain alkyl glycosides, the clearing points rise rapidly with increasing alkyl chain length. ,, The mesophase behavior of N -( n -alkyl)pyridinium hydrogen sulfates depends on the chain length n , increasing with n . The different results on chain length dependence are directly related to the mechanism of disorder.…”

“…Already in 1938, Knight and Shaw reported examples of liquid crystals of long-chain alkylpyridines . These cationic surfactants form thermotropic mesophases at relatively low temperatures (about 100 °C) . Most carbohydrate derivatives with one or two alkyl chains of sufficient length (usually C 6 or larger) form a mesophase upon heating. − Phosphorus catanionic amphiphiles ( catanionic phosphinate and phosphonate salts) form a liquid-crystalline thermotropic phase at high temperature (>180 °C) .…”

Thermal Behavior of Dodecylpyridinium-Based Surfactant Salts with Varied Anionic Constituent

“…51 Similar rich thermal behavior, i.e. polymorphism and mesomorphism was also obtained for the pyridinium compounds containing more than one linear alkyl chain, regardless of its length; N-(n-alkyl) pyridinium hydrogensulfates formed smectic B phases seen through fan shaped textures 24 , bis(N-alkyl pyridinium) tetrachlorocuprates exhibited hexagonal columnar 31 , cubic and smectic phases 31 , and hexadecylpyridinium based catanionic surfactants have shown rich thermotropic behavior with formation of smectic A and smectic B phases.…”