Journal Article

PUBDB-2019-03101

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Anomalous Dynamics of Concentrated Silica-PNIPAm Nanogels

Frenzel, L. (Corresponding author)DESY* ; Lehmkühler, F. (Corresponding author)DESY* ; Lokteva, I.DESY* ; Narayanan, S. ; Sprung, M.DESY* ; Grübel, G.DESY*

2019
ACS Washington, DC

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Please use a persistent id in citations: doi:10.1021/acs.jpclett.9b01690  doi:10.3204/PUBDB-2019-03101

Abstract: We present the structure and dynamics of highly concentrated core–shell nanoparticles composed of a silica core and a poly(N-isoproylacrylamide) (PNIPAm) shell suspended in water. With X-ray photon correlation spectroscopy, we are able to follow dynamical changes over the volume phase transition of PNIPAm at LCST = 32 °C. On raising the temperature beyond LCST, the structural relaxation times continue to decrease. The effect is accompanied by a transition from stretched to compressed exponential shape of the intensity autocorrelation function. Upon further heating, we find a sudden slowing down for the particles in their collapsed state. The q dependence of the relaxation time shows an anomalous change from $τ_c ∝ q^{–3}$ to $τ_c ∝ q^{–1}$. Small angle X-ray scattering data evidence a temperature-induced transition from repulsive to attractive forces. Our results indicate a temperature-induced phase transition from a colloidal liquid with polymer-driven dynamics toward a colloidal gel.

Note: © American Chemical Society

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Contributing Institute(s):

1. Coherent X-ray Scattering (FS-CXS)
2. Experimentebetreuung PETRA III (FS-PET-D)

Research Program(s):

1. 6215 - Soft Matter, Health and Life Sciences (POF3-621) (POF3-621)
2. DFG project 194651731 - EXC 1074: Hamburger Zentrum für ultraschnelle Beobachtung (CUI): Struktur, Dynamik und Kontrolle von Materie auf atomarer Skala (194651731) (194651731)
3. DFG project 390715994 - EXC 2056: CUI: Advanced Imaging of Matter (390715994) (390715994)

Experiment(s):

1. Measurement at external facility

Appears in the scientific report 2019

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Database coverage:
; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; IF >= 5 ; JCR ; NCBI Molecular Biology Database ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Web of Science Core Collection

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