Self-Consistent Theory for Structural Relaxation, Dynamic Bond Exchange Times, and the Glass Transition in Polymeric Vitrimers

Macromolecules, Journal Year: 2024, Volume and Issue: 57(7), P. 3242 - 3257

Published: March 28, 2024

We formulate a statistical mechanical theory for how dynamic bond exchange influences the activated hopping-driven relaxation of Kuhn segments in dynamically cross-linked networks or vitrimers over wide range temperatures and cross-link densities. The key new methodological aspect is to address self-consistent manner consequences on segmental alpha relaxation, vice versa. predicted temperature dependence time at high remains same as that permanent networks, but lower temperatures, significant acceleration occurs due exchanges. From mechanistic perspective, vitrimer local cage barrier very weakly affected by exchange, while collective elastic contribution decreases significantly deeply supercooled regime. glass transition grow linearly with square root density, previously found networks. Material-specific chemical effects such cross-linker size relative normal segment special attraction polymers are crudely considered based model calculations. quantitatively applied recent experiments dry ethylene vitrimers. Good agreements including follows an Arrhenius law enough upward non-Arrhenius deviations emerge regime, collapsed master curve exists densities temperatures. Possible extensions treat heterogeneity penetrant transport briefly discussed.

Language: Английский

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Facile Preparation of Tunable Polyborosiloxane Networks via Hydrosilylation

Chemistry of Materials, Journal Year: 2024, Volume and Issue: 36(12), P. 5935 - 5942

Published: June 4, 2024

Polyborosiloxanes are used in a variety of fields due to their unique dynamic properties. Traditionally, cross-linked polyborosiloxanes prepared by incorporating boric acid into siloxane prepolymers, process that is time-consuming, energy intensive, and challenging reagent immiscibility. Here, we report versatile synthetic method rapidly cure polyborosiloxane networks via hydrosilylation chain end or backbone functionalized polydimethylsiloxane (PDMS) derivatives with an inexpensive trivinylboronate. Networks synthesized from these readily available building blocks ∼2 min at convenient temperatures (e.g., 90 °C) exhibit enhanced viscoelastic behavior when compared traditional fabricated the conventional condensation route. By virtue using efficient chemistry, another key advantage this platform ability synthesize different network connectivity simply silicones Si–H moieties placed ends (end-group) distributed throughout repeat-unit structure (pendant-group). The availability other alkenes amenable provides additional formulation handle mixed dynamic–static tunable control over stress relaxation solvent resistance. In summary, approach disclosed herein simple accessible for preparing material

Language: Английский

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Molecular Dynamics Simulation and Theoretical Analysis of Structural Relaxation, Bond Exchange Dynamics, and Glass Transition in Vitrimers

Macromolecules, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 30, 2025

Language: Английский

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Decoupling Multiple Relaxation Modes: Composition and Distribution of Terminal Relaxation Time in Associative Polymers

Macromolecules, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 6, 2025

The distinctive rheological behavior of associative polymers (APs) is commonly attributed to the supramolecular interactions between stickers, where transient bonds are continually forming and breaking. This ongoing disruption reconstruction significantly extend terminal relaxation time, endowing APs with properties similar those entangled polymers. Based on fundamental sticky Rouse model (SRM), can be understood as a result combination strand motion interactions. However, this explanation may overly simplistic. presence multiple modes arising from broader range molecular processes introduces complexity, their individual contributions time remain uncertain. In work, we focus decoupling these modes. Our findings reveal that, beyond interactions, also influenced by factors such loss cross-links, reassociation dynamics, small molecule reactants. Furthermore, difference activation energy required for magnitude reaction kinetic stickers plays crucial role in determining distribution time. We believe that work offers significant insights into linear viscoelasticity (LVE) APs.

Language: Английский

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Self-healable fiber-reinforced vitrimer composites: overview and future prospects

RSC Advances, Journal Year: 2022, Volume and Issue: 12(50), P. 32569 - 32582

Published: Jan. 1, 2022

The article covers the outstanding features of fiber-reinforced vitrimer composites, including their reprocessing, recycling and self-healing properties.

Language: Английский

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