Local conservation law of rubber elasticity in hydrogel networks undergoing microphase separation and toughening

Xing, Ziyu, Lu, Haibao and Fu, Richard (2021) Local conservation law of rubber elasticity in hydrogel networks undergoing microphase separation and toughening. Polymer, 222. p. 123656. ISSN 0032-3861

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Official URL: https://doi.org/10.1016/j.polymer.2021.123656

Abstract

Thermoresponsive polymer segments have been reported to induce lateral microphase separations due to their switching transitions from a hydrophilic state to a hydrophobic one in hydrogels, which result in shrinkage and collapse of the polymer networks and significantly improved mechanical strength. However, the route from which the hydrophobic segments are assembled into micelles during microphase separations, and their thermoresponsive toughening mechanisms are not fully understood. In this study, a local conservation law of rubber elasticity is firstly formulated to describe the micellization and collapse of polymer networks in hydrogels, during which the thermoresponsive segments undergo a microphase separation. Flory-Huggins theory, interfacial free-energy equation and the extended Maxwell model are then employed to model the thermodynamics of micellization and microphase separations in the hydrogel, in which the polymer networks are composed of both hydrophilic and thermoresponsive segments. The toughening mechanism is further explored and discussed based on the proposed models. Finally, the proposed models have been verified using the experimental results reported in the literature. This study provides a new mechanism of local conservation law for rubber elasticity in hydrogels and also critical insights into the physical principles which govern the molecular self-assembly.

Item Type: Article
Additional Information: Funding information: This work was financially supported by the National Natural Science Foundation of China (NSFC) under Grant No. 11725208 and Newton Mobility Grant (IE161019) through Royal Society and NSFC.
Uncontrolled Keywords: hydrogel, rubber elasticity, microphase separation, micellization
Subjects: F200 Materials Science
F300 Physics
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: John Coen
Date Deposited: 15 Mar 2021 14:59
Last Modified: 28 Apr 2021 15:45
URI: http://nrl.northumbria.ac.uk/id/eprint/45700

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