Ionic Liquid Crystalline Systems Consisting of Polyammonium and Counter Carboxylate Ions

Shiori Tomitaka

doi:10.11648/j.am.20160506.13

Abstract

Novel ionic liquid crystals consisting of polyammonium and carboxylate ions were synthesized by ion complexation of polyethyleneimine and carboxylic acids (α,ω-dicarboxylic acids and hydroxyalkanoic acid). Their thermal properties and orientational behavior were examined by polarizing microscopic observation, differential scanning calorimetry, and variable temperature X-ray diffraction measurements. The ionic liquid crystals exhibited thermotropic liquid crystalline phases. The ionic liquid crystals (BP/ndA) bearing counter dicarboxylate ions formed a cubic phase upon heating and cooling. On the other hand, the ionic liquid crystal bearing the counter hydroxyalkanoate ion exhibited enantiotropic smectic A and smectic B phases with focal conic fan textures. These ionic liquid crystalline phases were formed by ionic and hydrophobic interactions because they did not have an aromatic mesogenic group.

Highlights

IntroductionThe noncovalent bond interaction, such as hydrogen bonding, donor-acceptor interaction, and ion interaction, plays an important role in the liquid crystal formation, thermal property, and orientation behavior
In liquid crystalline systems, the noncovalent bond interaction, such as hydrogen bonding, donor-acceptor interaction, and ion interaction, plays an important role in the liquid crystal formation, thermal property, and orientation behavior
The differential scanning calorimetry (DSC) curves for branched polyethyleneimine (BP)/ndA (n = 11, 13) indicated a secondary transition from a glass state to a liquid crystalline phase

Summary

Introduction

The noncovalent bond interaction, such as hydrogen bonding, donor-acceptor interaction, and ion interaction, plays an important role in the liquid crystal formation, thermal property, and orientation behavior. The ionic groups aggregate and segregate from the nonionic groups In such a case, a microphase separation occurs and induces liquid crystal formation. Ionic liquid crystalline systems without aromatic mesogenic groups were synthesized by ion complexation (a proton-transfer reaction) of polyethyleneimine and alkanoic acids [15, 16]. These ionic liquid crystalline systems exhibited a smectic A phase with an oily-streak texture and a homeotropic alignment upon heating and cooling. In the smectic A phase, which occurs due to a microphase separation through ionic interactions, a higher fluidity was observed This result showed that the proton-transfer reaction was a useful method to obtain these liquid crystalline systems. Shiori Tomitaka et al.: Ionic Liquid Crystalline Systems Consisting of Polyammonium and Counter Carboxylate Ions

Materials

Measurements

Thermal and Optical Properties

Structural Analysis

Conclusions