Temperature dependence of diffusion in 3-methylpentane/methylcyclohexane mixtures above their glass transition temperatures

Abstract

The temperature dependences of the phosphorescence decay from the triplet state of naphthalene embedded in 3- methylpentane/methylcyclohexane mixtures of different compositions in the presence and absence of oxygen have been determined and are presented as Arrhenius plots. In the presence of oxygen, the slopes of these plots above the glass transition temperature depend on the composition of the mixture. It is shown that the effect of solvent composition in this temperature region can be explained by interactions between the solvent molecules which affect the activation energy of diffusion of the oxygen which is quenching the triplet state of naphthalene.     In the absence of oxygen, the effect of solvent mixture composition is small, and it is suggested that the deactivation of the triplet state is affected by steric constraints imposed by the surrounding molecules.