Dynamics of the Topological Network Formed by Movable Crosslinks: Effect of Sliding Motion on Dielectric and Viscoelastic Relaxation Behavior
Yu Kashiwagi, Osamu Urakawa, Sheng Zhao, Yoshinori Takashima, Akira Harada, Tadashi Inoue
Abstract
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.