POS2-0628
Understanding Stress Relaxation in Covalent Adaptable Networks through Decoupled Kinetic and Diffusion Timescales
Topic
S2. High-End Characterization/Polymer Physics/Properties
When and Where
Sep 29, 2026
08:30 - 09:30
Room 301 (Grand Ballroom)
Session Chairs
Hae Jung SON
Boseok KANG
Presenter(s)
Yeomyung Yoon (Pusan National University)
Co-Author(s)
Abstract
Covalent adaptable networks (CANs) are reprocessable thermoset-like polymers that undergo network rearrangement through dynamic bond exchange. Although stress relaxation governs CAN processability and reprocessability, the molecular factors controlling relaxation behavior remain poorly understood. In particular, the overall relaxation time is determined by both the intrinsic exchange kinetics of dynamic bonds and the segmental mobility of the polymer network, which is strongly influenced by glass transition temperature (Tg).
Here, three disulfide-based CANs containing an identical dynamic crosslinker but different comonomers were investigated to elucidate the parameters governing stress relaxation. Temperature-dependent relaxation behavior was analyzed using a modified Maxwell model, enabling separation of the overall relaxation process into diffusion- and kinetic-timescales. The diffusion timescale was strongly dependent on comonomer chemistry and Tg, reflecting differences in segmental mobility and network constraints. In contrast, the kinetic timescale showed nearly identical temperature dependence for all systems, indicating that it is governed by the intrinsic disulfide exchange reaction.
The decoupled relaxation times revealed a transition from diffusion-controlled to exchange-controlled relaxation with increasing temperature. This transition corresponded to the onset of macroscopic network rearrangement and provided a physically meaningful definition of the topology-freezing transition temperature (Tv). Overall, this study establishes a quantitative framework linking dynamic bond exchange, Tg-controlled mobility, and macroscopic relaxation behavior, providing molecular design guidelines for tailoring CAN processability and reprocessability.
Here, three disulfide-based CANs containing an identical dynamic crosslinker but different comonomers were investigated to elucidate the parameters governing stress relaxation. Temperature-dependent relaxation behavior was analyzed using a modified Maxwell model, enabling separation of the overall relaxation process into diffusion- and kinetic-timescales. The diffusion timescale was strongly dependent on comonomer chemistry and Tg, reflecting differences in segmental mobility and network constraints. In contrast, the kinetic timescale showed nearly identical temperature dependence for all systems, indicating that it is governed by the intrinsic disulfide exchange reaction.
The decoupled relaxation times revealed a transition from diffusion-controlled to exchange-controlled relaxation with increasing temperature. This transition corresponded to the onset of macroscopic network rearrangement and provided a physically meaningful definition of the topology-freezing transition temperature (Tv). Overall, this study establishes a quantitative framework linking dynamic bond exchange, Tg-controlled mobility, and macroscopic relaxation behavior, providing molecular design guidelines for tailoring CAN processability and reprocessability.
