Multi-scale modeling of poly(isoprene) melts.pdf

a r X i v : c o n d - m a t / 0 0 1 0 2 9 3 v 1 [ c o n d - m a t .s o f t ] 1 9 O c t 2 0 0 0 Multi-scale modeling of poly(isoprene) melts Roland Faller? Florian Mu?ller-Plathe Max-Planck-Institut fu?r Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany February 1, 2008 Abstract Atomistic (atom-scale) and coarse-grained (meso-scale) simulations of structure and dynamics of poly-isoprene melts are compared. The lo- cal structure and chain packing is mainly determined by the atomistic details of the polymer architecture. The large-time dynamics encoun- tered in NMR experiments can be explained by meso-scale simulations including stiffness. The connecting link between the two scales is the stiffness which, although being a local property, influences strongly even the long-timescale dynamics. The standard reptation scenario fails to explain the observed dynamics. We propose strong reptation as a modified reptation scenario in which the local Rouse motion is absent. Keywords: Poly-isoprene, Modeling, Molecular Dynamics 1 Introduction The large abundance of polymers and their variety of applications make them an interesting target of study in theoretical material sci- ence. The understanding of the differences and similarities of the various materials is an important prerequisite for the goal of CAMD - computer aided materials design. The dream of chemical engineers would be to develop in the workstation the perfect material for a given purpose. ?present address: Department of Chemical Engineering, University of Wisconsin- Madison, 1415 Engineering Drive, Madison, WI 53706 1 To come closer to this distant goal, much effort in various fields is necessary. As polymeric materials are characterized by the im- portance of various length scales, the understanding of the interplay between these scales is of utmost importance. Methods adapted to all relevant scales are needed from the experimental as well as from the theoretical or simulational viewpoint. In simulati