Dynamic light scattering study on sliding mode of polyrotaxane solutions and slide-ring gels

We have reported the slide-ring gel (topological gel) synthesized using the polyrotaxane which consists of α-cyclodextrin and polyethylene glycol and have reported various physical properties. We have observed the polyrotaxane dissolved in sodium hydroxide aqueous solution using the dynamic-light- scattering method. In addition to the cooperative and translational modes observed in the usual polymer solutions, we found out the new kind of diffusion mode. Furthermore, we reported that this mode originated in sliding movement of cyclodextrin molecules on PEG chains. We call this mode "sliding mode". But, its mechanism was not known. We have improved the solubility of polyrotaxane by introducing hydroxypropyl groups to hydroxyl groups of cyclodextrin. We call it hydroxypropyl polyrotaxane (h-APR). In this study, we report cooperative, translational, and sliding mode as functions of concentration, scattering angle and temperature. We conclude that the sliding mode is cooperative diffusion mode based on sliding and colliding of cyclodextrin molecules on flexible random PEG network.