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Topological Decoupling of Association Kinetics and Viscoelasticity in Associative Star Polymers: A Sticky Rouse Model and Simulation Study
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DOI：10.1021/acs.macromol.6c00423.png)
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Abstract
En 中文
Associative polymers (APs) with star architectures offer a promising route to tailor the dynamics and mechanical properties of reversible polymer networks. However, establishing a predictive link between molecular topology and macroscopic viscoelasticity remains challenging. Here, we investigate the linear viscoelasticity (LVE) of unentangled associative star polymers by integrating the modified sticky Rouse model (SRM) and coarse-grained molecular simulations. By explicitly incorporating branched architectures into the SRM framework using graph theory, we derive analytical solutions for the LVE of star-shaped APs. To validate this approach and isolate the intrinsic topological contributions, we simulate well-defined vitrimer-like networks formed by unentangled telechelic star precursors using a hybrid Monte Carlo/molecular dynamics (hybrid MC/MD) algorithm. The simulation results exhibit quantitative agreement with theoretical predictions for stress relaxation and dynamic moduli, particularly in the terminal relaxation regime. We further reveal that star topology critically regulates terminal relaxation by modulating the local sticker encounter probability psc, which determines the bond lifetime τb through the prefactor τb0∼1psc. Specifically, increasing the arm length significantly reduces the local sticker density, thereby suppressing sticker encounters and dramatically retarding terminal relaxation, whereas increasing the arm number at fixed arm length has a much weaker effect. A universal scaling between the relative friction coefficient δ and terminal relaxation time τs (δ̃ ∼ τs) is observed across all investigated networks. These results show that branched architectures geometrically suppress sticker encounters and thereby decouple association-controlled terminal relaxation from internal strand motion, without changing the intrinsic exchange barrier prescribed in the model. Our work extends the universality of the SRM to topological APs, providing molecular-level guidelines for designing materials with tailored viscoelastic functions.
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5.2
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3.6W
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9.4W
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