Extreme thermodynamics with polymer gel tori: harnessing thermodynamic instabilities to induce large-scale deformations

When a swollen, thermoresponsive polymer gel is heated in a solvent bath, it expels solvent and deswells. When this heating is slow, deswelling proceeds homogeneously, as observed in a toroid-shaped gel that changes volume whilst maintaining its toroidal shape. By contrast, if the gel is heated quic...

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Bibliographic Details
Published in:arXiv.org 2018-06
Main Authors: Ya-Wen, Chang, Dimitriyev, Michael S, Souslov, Anton, Nikolov, Svetoslav V, Marquez, Samantha M, Alexeev, Alexander, Goldbart, Paul M, Fernandez-Nieves, Alberto
Format: Article
Language:English
Subjects:
Bimetals
Deformation mechanisms
Heating
Phase transitions
Polymers
Solvents
Thermodynamics
Toruses
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Summary:When a swollen, thermoresponsive polymer gel is heated in a solvent bath, it expels solvent and deswells. When this heating is slow, deswelling proceeds homogeneously, as observed in a toroid-shaped gel that changes volume whilst maintaining its toroidal shape. By contrast, if the gel is heated quickly, an impermeable layer of collapsed polymer forms and traps solvent within the gel, arresting the volume change. The ensuing evolution of the gel then happens at fixed volume, leading to phase-separation and the development of inhomogeneous stress that deforms the toroidal shape. We observe that this stress can cause the torus to buckle out of the plane, via a mechanism analogous to the bending of bimetallic strips upon heating. Our results demonstrate that thermodynamic instabilities, i.e., phase transitions, can be used to actuate mechanical deformation in an extreme thermodynamics of materials.
ISSN:2331-8422
DOI:10.48550/arxiv.1806.11049