Rotation of chromophores in amorphous polymer hosts of arbitrary disorder

Abstract

The rotational response of chromophores to an applied electric field is generalized for the case of an amorphous polymer host of arbitrary disorder. A time-dependent diffusion coefficient corresponding to a partially disordered system determines the solution of the rotational diffusion equation in response to the step function introduction of a poling field. This results in a transient that, in general, consists of two stretched exponential terms. In the limiting cases of complete order and disorder, the transient becomes a biexponential and a bi-power law, respectively. The degree of disorder is quantified to be consistent with the Scher–Montroll method of describing disorder in amorphous charge-transporting materials. Excellent agreement has been found between the theoretical dynamic and experimental measurement. This arbitrary disorder description is found to be consistently more accurate than assuming complete disorder. The effect of plasticization on the disorder is also studied.