Modelling of polymeric threading processes

Abstract

The threading of linear molecules through cyclic polymers was studied using rotational isomeric state and molecular modelling methods. The rotational isomeric state model calculated the proportions of cyclic poly(dimethylsiloxane) (PDMS) molecules with different ring sizes that could be threaded onto chain molecules of different diameters. It was found that the proportions threaded agreed quite well with topological trapping experiments. Molecular modelling was used to study the threading of cyclic PDMS molecules and the formation of rotaxanes. For each system studied the minimum energy of the molecules was measured as the linear molecule was translated through the cyclic molecule. The potential energy changes and the potential energy barriers during threading were found to be dependent on the type and size of the molecules studied. The minimum ring sizes for threading for two of the systems were found to agree with values determined experimentally.