Reptation and diffusive modes of motion of linear macromolecules

It is shown that the model of underlying stochastic motion of a macromolecule leads to two modes of motion: reptative and isotropically diffusive. There is a length of a macromolecule M* ≈ 10Me, where Me is “the macro-molecule length between adjacent entanglements,” above which macromolecules of a melt can be regarded as obstacles to motion of each other, and the macromolecules reptate. The transition to the reptation mode of motion is determined by both topological restrictions and local anisotropy of motion. The investigation confirm that the reptation motion determines the M−2 molecular-weight dependence of the self-diffusion coefficient of macromolecules in melts.