Coarse-Grained Polymer-Modelle und die Wiedereinführung der chemischen Details

For the computer simulation of polymers different time scale are necessary. One of the long standing challenges within the modeling of complex materials is to apply methods which allow to cover the range from microscopic to semimacroscopic regimes. In this work we introduce a systematic procedure to coarse grain atomistic polymer models into a mesoscopic model, which then allows an effective and fast simulation of melts. The method, which provides information on both static and dynamic properties, is tested for three different modifications of polycarbonate. For instance, the diffusion constant D could be measured by monitoring the mean square displacement of the monomers of the ehains or the center of gravity of the ehains, respectively. The models also successfully describe the variation in the Vogel Fulcher temperature as well as the total chain extension. The effective speedup compared to the corresponding atomistic simulation is significantly above 10$^{3}$After long simulation runs the chemical details are reintroduced into the coarse grained chains. The method is called $\textit{Inverse Mapping}$. A computer simulationand minimization of a polymer melt with all details of the chemical structure of the monomers is included. The resulting microscopic structure is compared to neutron scattering results by measuring the coherent scattering function. The remapping procedure is tested for two different polycarbonate modifications. It can be shown that there is a good agreement between the experimental and simulation data. Another part of the work deals with evaluation methods for structure functions. The computer simulation of coarse grained polymer melts enables us to compare the evaluation of neutron scattering data done by Debye fit and Zimm plot with the same evalution of the simulation data. In the simulation such values like the end-to-end distance can be measered directly. In this way the quality of the experimental evaluation methods can be determined