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Below is the abstract from the book cover: This thesis describes the dynamics of polymer melts as studied using computer simulation. The characteristic dynamics and viscoelastic behavior of a polymer melt are caused mainly by the fact that the polymer chains are coiled around each other and impede each other's motion: they are entangled. Because of heavy computational demands, fully atomistic molecular dynamics simulation is limited to relatively short chain lengths and time scales. In order to achieve longer time scales and chain lengths, the polymer chains are subdivided into coarse-grained particles, each of which represents the center of mass of a collection of consecutive monomers. When a fairly high level of coarse-graining is chosen, the interactions between the coarse-grained particles are, as a rule, so weak that the constraint of uncrossability of bonds is no longer automatically met. To prevent such unphysical bond crossings, a new uncrossability constraint is introduced. The author tests this method using polyethylene. Where relatively short chain lengths are concerned, the results of the coarse-grained simulations compare well with atomistic molecular dynamics simulations. These findings also compare well with experimental results for all chain lengths studied. The author concludes from an analysis of various dynamic correlation functions that the average chain in a polymer melt can be considered as moving inside a tube. He demonstrates that the diameter of this tube can consistently be derived in several different ways. |