Electron Spin Resonance Analysis for the Orientation and Dynamic Behavior of Nitroxy Radicals Modified by Stearic Acid in the Lamellar Liquid Crystal

Abstract

The electron spin resonance (ESR) spectra of n-doxylstearic acid (nNS : n=5, 7, 12, 16) in abinary system of 3- [2-hydroxy-3- (isooctadecyloxy) propoxy] -1, 2-propanediol (DGE) and water were measured to examine the behavior and orientation of nitroxy radicals modified by stearic acid in lamellar type liquid crystals (LC) formed by highly hydrophobic surface-active agents, such as alkyl glyceryl ethers. With increasing water content in LC, the order parameter of nNS (n=5, 7, 12) and correlation time of 16 NS decreased. Increment in the mobility of the DGE hydrophylic group by the addition of water would thus appear to influence the overall mobility of DGE molecules. A comparison of the relative mobility of each nNS indicated that the curvature of the DGE monolayer in contact with water in LC change continuously with increasing water content. The mobility of nNS in a DGE/water and GE/water system and changes in structure of lamellar type LC formed by DGE are thus demonstrated by the present results.