On the elastic nature of the demixing transition of aqueous PNIPAM solutions

Phillip, M.; Müller, Ulrich; Aleksandrova, Ralitsa; Sanctuary, Roland; Müller-Buschbaum, P.; Krüger, Jan-Kristian

doi:10.1039/c2sm26527c

Reference : On the elastic nature of 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/10993/12342

Title :	On the elastic nature of the demixing transition of aqueous PNIPAM solutions
Language :	English
Author, co-author :	Phillip, M. [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 :	2012
Journal title :	Soft Matter
Publisher :	Royal Society of Chemistry
Volume :	8
Pages :	11387-11395
Peer reviewed :	Yes (verified by ORBi^lu)
Audience :	International
ISSN :	1744-683X
e-ISSN :	1744-6848
City :	Cambridge
Country :	United Kingdom
Abstract :	[en] Mechanical instabilities accompanying the demixing transition of semi-dilute aqueous poly(Nisopropylacrylamide) (PNIPAM) solutions are probed for the first time with Brillouin spectroscopy, densitometry and refractometry. The particular role of the elastic moduli and the mass density at this coil-to-globule transition followed by molecular aggregation is investigated. Even though the demixing transition of PNIPAM solutions is denoted as a volume phase transition, it turns out that this transition is governed by the elastic properties, instead of the volume properties. This is consistent with earlier findings made for the demixing transition in chemically cross-linked PNIPAM hydrogels. Above the demixing temperature, Brillouin spectroscopy discriminates compact PNIPAM-rich agglomerates with sizes larger than 200 nm. Interestingly, these agglomerates possess a sharp distribution of elastic moduli, which can be attributed without any doubt to a material with gel-like mechanical consistency. Thus the phase-separated PNIPAM-rich agglomerates are not in the glassy state.
Permalink :	http://hdl.handle.net/10993/12342
DOI :	10.1039/c2sm26527c
Other URL :	www.rsc.org/softmatter

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