Fast local motions will be studied by molecular dynamics simulations. The results will be incorporated into the dynamic rotational isomeric state formalism in order to extend the time scale and the size of the systems examined. Two types of systems will be studied. The first type consists of polymeric hydrocarbons severely constrained by channels. Here the project will focus on the influence of torsional oscillations on the orientation autocorrelation functions, and the creation, lifetimes, migration, and destruction of conformational defects arising from independent, or correlated, conformational transitions. The second type of system consists of polyesters with a variety of spacers between aromatic units, and aromatic units that have fluorescence lifetimes shorter than, or longer than, the time scales of the molecular dynamics simulations. Fluorescence measurements will be performed for the polyesters under conditions where the internal dynamics is important. The overall objective is to increases the time scales, and the sizes of systems, susceptible to attack by atom-based studies of the internal dynamics. Polyesters are important industrial materials, and this research seeks to relate the motions of the molecules to the observed properties. Both computer modeling and critical experiments will be part of the investigation.
