Restricted Rotational Diffusion of Non-rigid Dumbbell-Type Macromolecules on Surfaces: Effects of the Bead-Bead and Bead-Surface Interaction

A recently derived Difusion equation [Uvarov A, Fritzsche S (2004) J Chem Phys 121(13):6561] is utilized to analyze the restricted rotational motion of macromolecules in solution if they are immobilized on a surface. Both, the bead-bead and bead-surface interactions are taken into account in order to describe the orientational dynamics of non-rigid macromolecules and its relaxation in time after a perturbation has occured. Using several realistic bead-bead and bead-surface potentials, detailed numerical investigations have been carried out for the rotational diffusion coefficient as well as for the conformational phase-space distribution function of the macromolecules. From this phase-space distribution, the orientational correlation function are derived and compared with phenomenological computations from the literature. Such correlation function can be observed in dielectric relaxation and fluorescence depolarization experiments.