Abstract
The influence of molecular stiffness on the dynamic properties of polymer melts is investigated analytically. It is shown that the relaxation times characterizing the internal dynamics of the polymer chains exhibit a crossover from Rouse to bending modes with increasing mode number. As a consequence the mean square displacement of monomers and the dynamic structure factor are strongly influenced by the molecular stiffness. The comparison of both equilibrium and dynamical properties of n-alkane chains in a melt with recent molecular dynamics simulations and neutron scattering experiments exhibits excellent agreement.