We present experiments and theory on the melt dynamics of monodisperse entangled polymers of H-shaped architecture. Frequency-dependent rheological data on a series of polyisoprene H-polymers are in good agreement with a tube model theory that combines path-length fluctuation (like that of star polymer melts) at high frequency, with reptation of the self-entangled “cross-bars” at low frequencies (like that of linear polymer melts). We account explicitly for mild polydispersity. Nonlinear step-strain and transient data in shear and extension confirm the presence of a relaxation time not seen in linear response, corresponding to the curvilinear stretch of the cross-bars. This time is very sensitive to strain due to the exponential dependence of the branch-point friction constants on the effective dangling path length. Strain-induced rearrangements of the branch points are confirmed by small-angle neutron scattering (SANS) on stretched and quenched partially deuterated samples. We develop an extension of melt-scattering theory to deal with the presence of deformed tube variables to interpret the SANS data.

We study the influence of topology on the extension of branched polymers subjected to external forces. Such forces can be applied mechanically (by micromanipulation techniques such as laser tweezers) or electrically (in the case of charged polymers). We focus on the unfold dynamics of star and dendrimer type structures. Some of the dynamical quantities of interest are: (i) the structural average of the mean monomer displacement, (ii) the elastic and the loss moduli and (iii) the mean displacement of a specified monomer. In a Gaussian‐type approach, (i) and (ii) depend only on the eigenvalues of the adjacency matrix whereas (iii) also requires the knowledge of the eigenvectors. Thus one can sometimes dispense with a full diagonalisation and use efficient recursion procedures. We highlight how the dynamic properties depend on topology: the number of branches and their length for stars and the number of generations for dendrimers. The intermediate time (crossover) behavior turns out to be most revealing of the underlying structure. We compare our results to those for fractal structures in external fields.

We study the stretch dynamics of flexible dendritic polymers (dendrimers and stars) under external forces. We work in the framework of the bead-spring model with hydrodynamic interactions (HI) and take spacers of different length into account. The applied fields may, e.g., be of mechanical or electrical 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 from the center of mass of the polymer) and also the elastic moduli. We analyze how these dynamic properties depend on the underlying topology, i.e., on the number of generations for dendrimers and the length and number of branches for stars. As a special point we assess in how far the HI method utilized 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 the stretch dynamics is for intermediate times close to logarithmic; hence the crossover in behavior at intermediate times is characteristic of the polymer’s topology.