Stretch dynamics of flexible dendritic polymers in solution

We study the stretch dynamics of flexible dendritic polymers (dendrimers an d stars) under external forces. We work in the framework of the bead-spring model with hydrodynamic interactions (HI) and take spacers of different le ngth into account. The applied fields may, e.g., be of mechanical or electr ical origin. We study the motion of a specific monomer, the time evolution of the stretch (the mean distance of the monomer on which the force acts fr om the center of mass of the polymer) and also the elastic moduli. We analy ze how these dynamic properties depend on the underlying topology, i.e., on the number of generations for dendrimers and the length and number of bran ches for stars. As a special point we assess in how far the HI method utili zed here (the Kirkwood-Riseman scheme) is stable for dendritic structures. Characteristic for the topology is the intermediate dynamics (between short and long times). It turns out that, different from stars, for dendrimers t he stretch dynamics is for intermediate times close to logarithmic; hence t he crossover in behavior at intermediate times is characteristic of the pol ymer's topology. (C) 2001 American Institute of Physics.