Thermotropic Phase Behavior of Choline Soaps
Regina Klein
Helen Dutton
Olivier Diat
Gordon J. T. Tiddy
Werner Kunz
10.1021/jp2006292.s001
https://acs.figshare.com/articles/journal_contribution/Thermotropic_Phase_Behavior_of_Choline_Soaps/2664139
Choline carboxylates (ChC<i>m</i> with <i>m</i> = 12−18) are simple biocompatible anionic surfactants with very low Krafft temperatures, possessing a rich aqueous phase behavior. In the present work, we have investigated the thermotropic mesomorphism of anhydrous ChC<i>m</i> salts for <i>m</i> = 12−18. Transition temperatures and enthalpies determined by differential scanning calorimetry reveal that all investigated compounds exhibit three different phases between −20 and 95 °C. The phases were further characterized by optical polarizing microscopy, NMR spin−spin relaxation, and X-ray scattering measurements. The nature of the phases was identified with increasing temperature as crystalline, semicrystalline, and liquid−crystalline lamellar. Even long-chain choline carboxylates (<i>m</i> = 18) were found to melt into a lamellar liquid−crystalline phase below 100 °C. Accordingly, with choline as counterion in simple fatty acid soaps, not only the water solubility is considerably enhanced but also the melting points are substantially reduced, hence facilitating thermotropic mesomorphism at temperatures between 35 and 95 °C. Thus, simple choline soaps with <i>m</i> = 12−18 may be classified as ionic liquids.
2011-04-14 00:00:00
Choline SoapsCholine carboxylates
ChCm
thermotropic mesomorphism
choline
phase
Thermotropic Phase Behavior
lamellar
NMR