Investigation of Volume Absorption Anisotropy of Complex Anisotropic Structures

Abstract

Linear polyconjugated π-systems are rod-like molecular structures possessing mesogenic properties. Oriented layers of such materials demonstrate dichroic absorption of light. Prevailing absorption along long molecular axis of π-system, gives ground to study molecular distribution in the layer though polarizer light absorption. We derived equations to investigate light propagation in the layer with anisotropic absorption. If principle axes are known, series of polarized absorption spectra measurements in combination with sample rotation allow to measure volume absorption of the layer along x-, y-, z- axes to determine s_x, s_y, and s_z order parameters of complex anisotropic structure. We investigated molecular reorientation dynamic of azo dyes (Reversible Intermolecular Bonding photoalignment materials) upon polarized light exposure. According to experimental results, for layers with thickness below quarter wavelength of observation, the Pointing vector (light energy) propagate through absorbing anisotropic structure without refraction, while at thickness few times greater the wavelength of observation, refraction is observed.

Keywords:

• Absorption anisotropy
• anisotropic structure
• volume anisotropy