Influence of Interaction Strength on the Energy Dissipation and Viscoelasticity of Transient Polymer Networks

초록

Transient polymer networks cross-linked by reversible bonds offer an innovative balance of adaptability and mechanical robustness, yet translating molecular-level association energies into macroscopic viscoelasticity remains challenging. Here, we utilize coarse-grained molecular dynamics simulations to systematically investigate highly cross-linked transient networks, directly comparing them with a permanently cross-linked static network. We demonstrate that tuning the thermodynamic association strength of the transient cross-links (epsilon) governs the intrinsic bond lifetimes, and the resulting kinetic competition between this lifetime and the observation time frame fundamentally dictates the network's mesoscopic architecture and macroscopic energy dissipation mechanisms. Strong physical interactions (epsilon = 10k B T) drive the formation of bulky multiplet nodes, inducing severe dynamic heterogeneity and a strong "cage effect". Under large deformation, this leads to time-driven topological restructuring, yielding superior stiffness, robust cluster alignment, and large energy dissipation without catastrophic yielding. Conversely, moderately associating networks (epsilon = 5k B T) exhibit strain-driven dynamic yielding via continuous bond exchange, enabling topological remodeling and fluid-like transitions characterized by a distinct viscoelastic crossover. These molecular-level insights provide a quantitative framework for designing advanced soft materials, demonstrating how specific noncovalent interaction strengths can be engineered to precisely control the trade-off between structural resilience and dynamic adaptability.

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