Dynamics of Semiflexible Dendrimers in Dilute Solutions

The dilute solution dynamic properties of dendrimers are theoretically studied in the framework of an optimized Rouse-Zimm approach. Semiflexibility is implemented by modeling topological restrictions on the directions and orientations of the respective bond vectors. This accounts for the neglect of excluded volume interactions in the limit of short spacers. The transport properties, particularly, the behavior of intrinsic viscosity and translational diffusion coefficient are analyzed as functions of flexibility and dendrimer generational growth. The intrinsic viscosity reveals a characteristic maxima, as is experimentally observed in some cases. The value and position of the maxima varies with the topology of the molecule and is mainly dictated by the longest relaxation times. The diffusion coefficient shows a steady decrease for all topologically different conformations up to the fourth generation. The inclusion of hydrodynamic interactions accelerates the dynamics of all semiflexible dendrimer models by decreasing the respective range of intrinsic viscosity and diffusion coefficient values. The structural differences between the different conformations are manifest in the subsequent generations. These topologically dependent flexibility parameters provide suitable approximations to explore the intramolecular dynamics of real dendrimers.