Decoupled Main-Chain and Sticker Dynamics in Associating Comb Polymers*

Associating polymer containing polar, acidic or ionic groups enable the design of responsive materials. Elucidating the lifetime (τ) and activation energy (E_a) of sticker association/dissociation is important in designing associating polymers. In this study of novel associating comb polymers, we use electrochemical impedance spectroscopy (EIS) to reveal an unexpected bifurcation of the subsegmental dynamics. This discovery enables us to directly measure the intrinsic τ and E_a of sticker association/dissociation process. This glassy phenomenon is attributed to the decoupled motions between the sulfur linkages adjacent to the backbone and the acid-terminated pendants and defines a new dynamic parameter, the bifurcation temperature T_b. T_b correlates strongly with the glass transition temperature (T_g) that is predominantly determined by pendant length rather than sticker concentration. Our results elucidate the critical role of polymer architecture and pendant length in the structural relaxations of glassy associating polymers.