Electron resonance investigation of a cholesteric mesophase induced by a chiral probe

Abstract

An induced cholesteric phase has been produced by dissolving the chiral nitroxide probe 5α-cholestane-3-spiro-2′-N′-oxyl-3′,3′-dimethyloxazolidine in the nematic phase of 4,4′-bis-n-heptylazoxy-benzene (HEPTAB). The chiral solute has been studied by e.s.r., and order parameters and correlation times obtained by spectral simulation using angular-dependent linewidth theory. Inhomogeneous broadening has been taken into account by using a Voigt convolution lineshape function. The unwinding of the induced cholesteric helix when cooling to the smectic phase has been followed, and the distortion parameter for the helix has been determined at various temperatures.