Simulations of phase transitions in macromolecular systems

The study of phase transitions in concentrated solutions and melts of flexible or stiff polymers is a computational challenge for computer simulations, since already a single polymer coil exhibits nontrivial structure from the scale of a chemical bond (1 A) to the coil radius (100 Angstrom), and for the simulation of collective phenomena huge simulation boxes containing many polymers are required. A strategy to deal with this problem is the use of highly coarse-grained models on a lattice, such as the bond fluctuation model. Several studies employing such models will be briefly reviewed, e.g.: temperature-driven isotropic-nematic phase transition in concentrated solutions of semiflexible polymers, unmixing of polymer blends in the bulk and in a geometry confined between walls which prefer one component. It is shown that the finite-size scaling techniques previously developed for Ising-type models are useful in this context, too. Simulation of unmixed polymer blends between competing walls allows a study of an interface localization-delocalization transition and the observations of anomalous interfacial broadening, (depending on thin film thickness). These simulations have also elucidated experiments. (C) 2002 Elsevier Science B.V. All rights reserved.