Reference : Immense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions

	Document type :	Scientific journals : Article
	Discipline(s) :	Physical, chemical, mathematical & earth Sciences : Physics
	To cite this reference:	http://hdl.handle.net/10993/13878

Title :	Immense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions
Language :	English
Author, co-author :	Philipp, Martine [Technische Universität München - TUM]
	Müller, Ulrich [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
	Aleksandrova, Ralitsa [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
	Sanctuary, Roland [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
	Müller-Buschbaum, P. [Technische Universität München - TUM]
	Krüger, Jan-Kristian [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
Publication date :	2013
Journal title :	Soft Matter
Publisher :	Royal Society of Chemistry
Volume :	9
Pages :	5034-5041
Peer reviewed :	Yes (verified by ORBilu)
Audience :	International
ISSN :	1744-683X
e-ISSN :	1744-6848
City :	Cambridge
Country :	United Kingdom
Abstract :	[en] Elastic nonlinearities are particularly relevant for soft materials because of their inherently small linear elasticity. Nonlinear elastic properties may even take over the leading role for the transformation at mechanical instabilities accompanying many phase transitions in soft matter. Because of inherent experimental difficulties, only little is known about third order (nonlinear) elastic constants within liquids, gels and polymers. Here we show that a key concept to access third order elasticity in soft materials is the determination of mode Gr¨uneisen parameters. We report the first direct observation of third order elastic constants across mechanical instabilities accompanying the liquid–liquid demixing transition of semi-dilute aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions. Immense elastic nonlinearities, leading to a strong strain-softening in the phase-separating PNIPAM solutions, are observed. Molecular mechanisms, which may be responsible for these immense elastic nonlinearities, are discussed. The importance of third order elastic constants in comparison to second order (linear) elastic constants in the demixing PNIPAM solutions evidences the need to focus more on the general role played by nonlinear elasticity at phase transitions within synthetic and biological liquids and gels.
Permalink :	http://hdl.handle.net/10993/13878
DOI :	10.1039/c3sm00034f
Other URL :	www.rsc.org/softmatter

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