Orientational order and dynamics of fluorescent probes in aligned lyotropic phases by fluorescence depolarization spectroscopy. Perylene in a nematic discotic phase. A comparison with ²H NMR

Abstract

The orientational order and dynamics of perylene in the nematic discotic phase (N_dII) of the potassium laurate/KCl/decanol/water system has been investigated by fluorescence depolarization (FD) spectroscopy. The order parameters of perylene-d ₁₂ in the same phase had been previously determined by ²H NMR. FD experiments were performed with the phase-modulation technique in the temperature range between 10°C and 50°C. At each temperature we could determine <P ₂> and <P ₄> for the axis of the transition moments of perylene, together with the rotational correlation time Θ_R. All these quantities assume reasonable values and show regular trends as functions of temperature. In particular, <P ₂> is in good agreement with that determined by ²H NMR.