Orientational diffusion of the toluene-d3methyl group in solutions and polymer matrices

Abstract

IR spectra of solutions of selectively deuterated toluene C6H5CD3 in the region of the asymmetric stretching vibrations of the CD3 group are studied. Pentane, non-deuterated toluene, dibutyl phthalate, acetone and polymers: polybutadiene (PBD), polypropylene (PP) and polymethyl methacrylate (PMMA) are used as solvents. In order to determine activation enthalpy ΔH* and entropy ΔS* of the orientational diffusion of the CD3 group the temperature dependencies of the absorption band widths δ of the asymmetric vibrations of this group are studied. An original method of estimating the errors in determining the values ΔH* and ΔS* within Rakov's approach is propsed and checked. The values obtained for ΔH* do not exceed 1 kcal mol-1. No correlation of ΔH* with either the dielectric permittivity or the viscosity of the medium was observed. The glass transition in dibutyl phthalate and PBD, as well as relaxation transitions in PP and PMMA, do not affect the dependence δ ={cauchy integral}(T). © 1993.