Advances and New Opportunities in the Rheology of Physically and Chemically Reversible Polymers

• Published in: Macromolecules Vol. 55; no. 3; pp. 697 - 714
• Main Authors: Wu, Shilong, Chen, Quan
• Format: Journal Article
• Language: English
• Published: American Chemical Society 08.02.2022
• Subjects: chemical species; crosslinking; dissociation; gelation; Gibbs free energy; rheology; thermal energy; viscoelasticity
• ISSN: 0024-9297; 1520-5835; 1520-5835
• DOI: 10.1021/acs.macromol.1c01605

The advances in understanding the dynamics of both the physically and chemically reversible networks are summarized from a rheological perspective. The focus is placed on linear viscoelasticity, which is related to thermodynamics and reversible kinetics at quasi-equilibrium states. We first explain basic assumptions and predictions of the reversible-network theories, including the reversible gelation, sticky-Rouse, and sticky-reptation theories. We then summarize the dynamic features of the state-of-the-art materials that have not been fully incorporated into the current theoretical framework: (1) cooperative motion of the nearby stickers significantly increases the dissociation energy of physically reversible networks, (2) the degree of gelation becomes highly T-dependent when the Gibbs free energy approaches the thermal energy for both the physically and chemically reversible networks, and (3) the exchange rate of dynamic cross-links of chemically reversible networks is reaction-controlled and depends on the chemical species and concentrations of the reactants. Finally, some pathways for future theoretical development are suggested.