Detection Of Hexagonal Phases by Esr Spin Labeling

The potential of ESR spin labeling in determining hexagonal amphiphilic phases is assessed. Spin labeled hexagonal phases in which the motional averaging about the cylinder axis is rapid on the ESR time scale can be readily identified by their ESR spectrum. The lineshape is distinctly different from that of smectic lamellar phases. The same ESR lineshape which is characteristic of the hexagonal phase is also obtained with spin labeled rodlike micelles provided that the motional averaging about their cylinder axis is rapid. If, however, this averaging is slow both hexagonal phases and rodlike micelles give ESR spectra which are indistinguishable from smectic phases (disclike micelles).