Molecular dynamics and structure of polyrotaxane in solution

Abstract

Polyrotaxane (PR) is a supramolecular assembly in which ring molecules are threaded onto an axial polymer chain. This paper reviews the molecular structure and dynamics of a PR composed of polyethylene glycol (PEG) and α-cyclodextrin (CD) based on data obtained from X-ray and neutron scattering experiments on PR solutions. The dynamics of CD and the PEG monomers in the PR were evaluated separately by quasielastic neutron scattering with deuterium labeling. Inclusion complex formation with CD increases the stiffness of the PEG backbone and restricts the diffusion of the PEG monomers that are covered by or in close proximity to the CD molecules. The sliding motion of the CD molecules along the PEG axis was explored using full atomistic molecular dynamics (MD) simulations, showing that the sliding dynamics were retarded by the interaction between the CD cavities and PEG. This paper reviews our X-ray and neutron scattering experiments on the molecular structure and dynamics of a supramolecular assembly, polyrotaxane (PR) composed of polyethylene glycol (PEG) and α-cyclodextrin (CD). Inclusion complex formation with CDs increases the stiffness of the PEG backbone and restricts the diffusion of the PEG monomers that are covered by or in close proximity to the CD molecules.