Journal Article

PreJuSER-12073

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Yielding processes in a colloidal glass of soft star-like micelles under large amplitude oscillatory shear (LAOS)

Renou, F. ; Stellbrink, J.FZJ* ; Petekidis, G.

2010
Inst. Melville, NY [u.a.]

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Please use a persistent id in citations: http://hdl.handle.net/2128/18117  doi:10.1122/1.3483610

Abstract: The understanding of yielding and flow of a colloidal glass under large amplitude oscillatory shear (LAOS) represents a motivating challenge. Monitoring the higher harmonics in the stress signal by Fourier-transform (FT) rheology may provide useful insight on the progressive transition from linear to nonlinear viscoelastic response. However, the physical interpretation of FT-rheology data is still not obvious. Here we study the process of yielding in a colloidal glass formed by star-like block copolymer micelles with LAOS experiments and interrogate the nonlinear intracycle stress response by FT analysis and decomposition to an orthogonal set of Chebyshev polynomials [Ewoldt, R. H., et al. J. Rheol. 52(6), 1427-1458 (2008)]. Such approach provides a robust framework enabling us to map out a rich phenomenology of intracylce nonlinearities that may relate to distinct physical mechanisms. We find that the nonlinearities during yielding are represented by intracylce shear thickening/thinning and strain hardening/softening of the viscous and elastic response of the system, respectively. We suggest that the underlying mechanisms are related to cage breaking and reformation as well as stress storing and relaxation within the period of oscillatory shear which are affected by an interplay between shear and Brownian motions and thus relate to Peclet number variation with strain and frequency. (C) 2010 The Society of Rheology. [DOI: 10.1122/1.3483610]

Keyword(s): J

Note: We thank Nikos Koumakis and Andreas Poulos for valuable discussions and technical assistance and Simon Rogers for fruitful discussions. We also acknowledge Randy Ewoldt for providing the MITLAOS software for the Chebyshev decomposition. This work has been supported by the EU funding through NoE Softcomp, ToK Cosines, and NMP SMALL Nanodirect. J.S. acknowledges DFG for support via SFB-TR6.

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Contributing Institute(s):

1. Neutronenstreuung (IFF-5)
2. Streumethoden (IFF-4)
3. JCNS (Jülich Centre for Neutron Science JCNS (JCNS) ; JCNS)

Research Program(s):

1. BioSoft: Makromolekulare Systeme und biologische Informationsverarbeitung (P45)
2. Großgeräte für die Forschung mit Photonen, Neutronen und Ionen (PNI) (P55)

Appears in the scientific report 2010

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