Dynamics of the Topological Network Formed by Movable Crosslinks: Effect of Sliding Motion on Dielectric and Viscoelastic Relaxation Behavior

We investigated the dynamics of the topological network formed by rotaxane-type movable crosslinks consisting of a poly(ethyl acrylate) backbone threaded through peracetylated cyclodextrins, which are connected to other chains. We used rheological and broadband dielectric spectroscopy measurements to analyze the dynamics on various time and length scales. The movable crosslink was found to affect the overall network dynamics in two different time scales. In the terminal region, it acted as a long-lived crosslink, delaying or inhibiting the flow of the system. In the glass-to-rubber transition region where network strand dynamics is responsible, a new relaxation process called slow mode was clearly detected, especially in dielectric spectroscopy. We ascribed this relaxation to the rotational motion of the rotaxane-type cyclodextrin moieties via sliding on the polymer backbone accompanied by the chain conformational change. A possible mechanism of the slow mode and its relationship with the segmental and chain relaxations are discussed.

Automated summary

The study found that movable crosslinks have different effects on the dynamics of the network in two time scales, delaying or inhibiting the flow of the system. A new relaxation process called slow mode was detected in the glass-to-rubber transition region, which is attributed to the rotational motion of rotaxane-type cyclodextrin moieties along the polymer backbone.