Abstract
Thermal properties of smectic liquid crystals of dimyristoylphosphatidylglycerol sodium salt (DMPG) in water were investigated as a function of temperature above the gel-liquid crystal transition temperature, Tm, by X-ray diffraction analysis of the repeat distance of the bilayer, differential scanning calorimetry (DSC) for phase transition, the hyperfine splitting constant in electron spin resonance (ESR) method with spin probes and equilibrium spreading pressure. The data obtained were found to differ remarkably below and above the critical temperature T* (=31.7°C) for DMPG bilayers. The weakening of hydration of terminal glycerol moiety in DMPG at T*, with consequently enhanced microflexibility of DMPG bilayers above this temperature may be explanation for these differences. The effects of dehydration of the terminal glycerol moiety on surface activity was confirmed from the temperature dependence of equilibrium spreading pressure of DMPG.
