Polarization of Molecular Luminescence in Plastic Media by the Method of Photoselection

Abstract

In the method of photoselection for measuring molecular polarization, it is not necessary that the molecule be embedded in a crystal of known structure, but merely rigidly fixed in a random arrangement. In this paper the possibility of using a plastic as the host solvent is examined. This would replace the previously used mixtures of organic solvents that form glasses at 77°K, and which, because of experimental conditions, might give rise to great depolarization effects. In methyl methacrylate polymer (Lucite), the phosphorescence of phenanthrene, coronene, and pyrazine is found to be polarized at room and liquid-nitrogen temperatures. The measured degree of polarization in the plastic is found to be in good agreement with the expected value. The effect on the degree of polarization of temperature, concentration, thickness, and shape of the plastic sample is discussed. The importance of using this method for further polarization investigations to increase our understanding of the structure and spectroscopic properties of complex luminescent guest molecules, as well as the internal structure and motions of different host polymers, is pointed out.