Thermotropic Liquid Crystals from Hydrogen-Bonded Amphiphiles: N-Alkyl-Substituted Iminodiacetic Acids

Abstract

Alkyl derivatives of iminodiacetic acid, i.e. CH₃(CH₂) _n−1N(CH₂COOH)₂, with n = 12, 14, 16, 18, were studied by polarizing optical microscopy, differential scanning calorimetry, and x-ray diffraction. They were found to exhibit liquid crystalline behavior and specifically to produce disordered smectic phases above about 130°C. Observed for the first time with saturated aliphatic acids, the smectic ordering may be attributed to the intramolecular segregation of the alkyl chains from the polar zwitterionic iminodiacetic endgroups which interact through hydrogen boding and coulombic forces.

Key Words:

• N-alkyl-iminodiacetic acid derivatives
• hydrogen-bonded amphiphiles
• lipophilic and hydrophilic moieties
• thermotropic liquid crystals