Negative Energy Elasticity in a Rubberlike Gel

Rubber elasticity is the archetype of the entropic force emerging from the second law of thermodynamics; numerous experimental and theoretical studies on natural and synthetic rubbers have shown that the elasticity originates mostly from entropy change with deformation. Similarly, in polymer gels co...

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Autores principales:	Yuki Yoshikawa, Naoyuki Sakumichi, Ung-il Chung, Takamasa Sakai
Formato:	article
Lenguaje:	EN
Publicado:	American Physical Society 2021
Materias:	Physics QC1-999
Acceso en línea:	https://doaj.org/article/65640ab58e9e4fe0bf423b692827f939
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spelling	oai:doaj.org-article:65640ab58e9e4fe0bf423b692827f9392021-12-02T17:06:52ZNegative Energy Elasticity in a Rubberlike Gel10.1103/PhysRevX.11.0110452160-3308https://doaj.org/article/65640ab58e9e4fe0bf423b692827f9392021-03-01T00:00:00Zhttp://doi.org/10.1103/PhysRevX.11.011045http://doi.org/10.1103/PhysRevX.11.011045https://doaj.org/toc/2160-3308Rubber elasticity is the archetype of the entropic force emerging from the second law of thermodynamics; numerous experimental and theoretical studies on natural and synthetic rubbers have shown that the elasticity originates mostly from entropy change with deformation. Similarly, in polymer gels containing a large amount of solvent, it has also been postulated that the shear modulus (the modulus of rigidity) G, which is a kind of modulus of elasticity, is approximately equivalent to the entropy contribution G_{S}, but this has yet to be verified experimentally. In this study, we measure the temperature dependence of the shear modulus G in a rubberlike (hyperelastic) polymer gel whose polymer volume fraction is at most 0.1. As a result, we find that the energy contribution G_{E}=G-G_{S} can be a significant negative value, reaching up to double the shear modulus G (i.e., \|G_{E}\|≃2G), although the shear modulus of stable materials is generally bound to be positive. We further argue that the energy contribution G_{E} is governed by a vanishing temperature that is a universal function of the normalized polymer concentration, and G_{E} vanishes when the solvent is removed. Our findings highlight the essential difference between rubber elasticity and gel elasticity (which were previously thought to be the same) and push the established field of gel elasticity into a new direction.Yuki YoshikawaNaoyuki SakumichiUng-il ChungTakamasa SakaiAmerican Physical SocietyarticlePhysicsQC1-999ENPhysical Review X, Vol 11, Iss 1, p 011045 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Physics QC1-999
spellingShingle	Physics QC1-999 Yuki Yoshikawa Naoyuki Sakumichi Ung-il Chung Takamasa Sakai Negative Energy Elasticity in a Rubberlike Gel
description	Rubber elasticity is the archetype of the entropic force emerging from the second law of thermodynamics; numerous experimental and theoretical studies on natural and synthetic rubbers have shown that the elasticity originates mostly from entropy change with deformation. Similarly, in polymer gels containing a large amount of solvent, it has also been postulated that the shear modulus (the modulus of rigidity) G, which is a kind of modulus of elasticity, is approximately equivalent to the entropy contribution G_{S}, but this has yet to be verified experimentally. In this study, we measure the temperature dependence of the shear modulus G in a rubberlike (hyperelastic) polymer gel whose polymer volume fraction is at most 0.1. As a result, we find that the energy contribution G_{E}=G-G_{S} can be a significant negative value, reaching up to double the shear modulus G (i.e., \|G_{E}\|≃2G), although the shear modulus of stable materials is generally bound to be positive. We further argue that the energy contribution G_{E} is governed by a vanishing temperature that is a universal function of the normalized polymer concentration, and G_{E} vanishes when the solvent is removed. Our findings highlight the essential difference between rubber elasticity and gel elasticity (which were previously thought to be the same) and push the established field of gel elasticity into a new direction.
format	article
author	Yuki Yoshikawa Naoyuki Sakumichi Ung-il Chung Takamasa Sakai
author_facet	Yuki Yoshikawa Naoyuki Sakumichi Ung-il Chung Takamasa Sakai
author_sort	Yuki Yoshikawa
title	Negative Energy Elasticity in a Rubberlike Gel
title_short	Negative Energy Elasticity in a Rubberlike Gel
title_full	Negative Energy Elasticity in a Rubberlike Gel
title_fullStr	Negative Energy Elasticity in a Rubberlike Gel
title_full_unstemmed	Negative Energy Elasticity in a Rubberlike Gel
title_sort	negative energy elasticity in a rubberlike gel
publisher	American Physical Society
publishDate	2021
url	https://doaj.org/article/65640ab58e9e4fe0bf423b692827f939
work_keys_str_mv	AT yukiyoshikawa negativeenergyelasticityinarubberlikegel AT naoyukisakumichi negativeenergyelasticityinarubberlikegel AT ungilchung negativeenergyelasticityinarubberlikegel AT takamasasakai negativeenergyelasticityinarubberlikegel
_version_	1718381556452556800

Negative Energy Elasticity in a Rubberlike Gel

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