Parts | Days | Selection | Search | Downloads | Help

SYCN: Computational nanoscience - from materials to biology

SYCN 101: Computational Nanoscience: From Materials to Biology (Hauptvortr
äge)

SYCN 101.3: Invited Talk

Tuesday, March 25, 2003, 15:30–16:00, ZEU/160

Simulation studies of polymerization: from energy and reaction mechanisms to the macroscopic limit — •Pietro Ballone^1,2, Jaakko Akola², and Robert O. Jones² — ¹University of Messina, I-98166 Messina, Italy — ²Institut f"ur Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany

The mechanical and thermal properties of complex materials, as well as their phase diagrams, provide demanding tests of multi-approach computational methods covering a wide range of length and time scales. Examples are provides by density functional calculations of regular and defect structures, potential energy, and reactivity for organic systems closely related to bisphenol-A-polycarbonate (BPA-PC). The results provide the basis for a model describing the ring-opening polymerization of its cyclic oligomers by nucleophilic molecules. Monte Carlo simulations using this model show a strong tendency to polymerize that is increased by increasing density, temperature and dimensionality (2D to 3D). Entropy in the distribution of inter-particle bonds is the driving force for chain formation, with potential energy and vibrational entropy playing only a minor role. Branching centers reduce the degree of polymerization at low concentration, but they result at high concentrations in a space filling gel.