Inclusion Complexes of Chain Molecules with Cycloamyloses. 2. Molecular Dynamics Simulations of Polyrotaxanes Formed by Poly(ethylene glycol) and α-Cyclodextrins

Molecular dynamics (MD) simulations were performed for “channel type” polyrotaxanes with α-cyclodextrins (α-CDs) threaded onto monodisperse chains of poly(ethylene glycol) (PEG). The polymer captures as much α-CD as its length permits, forming a close-packed structure from the one end to the other. The van der Waals interactions are the main source of the stabilization of these polyrotaxanes. Hydrogen bonds between successive α-CDs slightly favor head-to-head, tail-to-tail sequences over head-to-tail sequences. The α-CDs in polyrotaxanes are more symmetric and less distorted than the isolated α-CDs. The PEG in the polyrotaxane is more extended than an unperturbed chain, because it has a larger population of trans states at internal bonds.