Journal Article

PreJuSER-19771

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Polymer Dynamics in responsive microgels: influence of cononsolvency and microgel architecture

Scherzinger, C. ; Holderer, O.FZJ* ; Richter, D.FZJ* ; Richtering, W.

2012
RSC Publ. Cambridge

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Please use a persistent id in citations: http://hdl.handle.net/2128/7401  doi:10.1039/c2cp23328b

Abstract: The dynamics of polymers on the nm and ns scales inside responsive microgels was probed by means of Neutron Spin Echo (NSE) experiments. Four different microgels were studied: poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-diethylacrylamide) (PDEAAM) microgels, a P(NIPAM-co-DEAAM) copolymer microgel and a core-shell microgel with a PDEAAM core and a PNIPAM shell. These four different microgel systems were investigated in a D(2)O/CD(3)OD solvent mixture with a molar CD(3)OD fraction of x(MeOD) = 0.2 at 10 °C. The PNIPAM and the P(NIPAM-co-DEAAM) microgels are in the collapsed state under these conditions. They behave as solid diffusing objects with only very small additional contributions from internal motions. The PDEAAM particle is swollen under these conditions and mainly Zimm segmental dynamics can be detected in the intermediate scattering function at high momentum transfer. A cross-over to a collective diffusive motion is found for smaller q-values. The shell of the PDEAAM-core-PNIPAM-shell particle is collapsed, which leads to a static contribution to S(q,t); the core, however, is swollen and Zimm segmental dynamics are observed. However, the contributions of the Zimm segmental dynamics to the scattering function are smaller as compared to the pure PDEAAM particle. Interestingly the values of the apparent solvent viscosities inside the microgels as obtained from the NSE experiments are higher than for the bulk solvent. In addition different values were obtained for the PDEAAM microgel, and the PDEAAM-core of the PDEAAM-core-PNIPAM-shell particle, respectively. We attribute the strongly increased viscosity in the PDEAAM particle to enhanced inhomogeneities, which are induced by the swelling of the particle. The different viscosity inside the PDEAAM-core of the PDEAAM-core-PNIPAM-shell microgel could be due to a confinement effect: the collapsed PNIPAM-shell restricts the swelling of the PDEAAM-core and may modify the hydrodynamic interactions in this restricted environment inside the microgel.

Keyword(s): Basic research (1st) ; Others (1st) ; Soft Condensed Matter (2nd) ; J

Note: This research project has been supported by the European Commission under the 7th Framework Programme through the Key Action: Strengthening the European Research Area, Research Infrastructures. Contract no.: 226507 (NMI3). This work is based on experiments performed at the Julich Centre for Neutron Science JCNS, Forschungszentrum Julich, Germany.

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Contributing Institute(s):

1. Neutronenstreuung (ICS-1)
2. Neutronenstreuung (JCNS-1)
3. JCNS-FRM-II (JCNS (München) ; Jülich Centre for Neutron Science JCNS (München) ; JCNS-FRM-II)

Research Program(s):

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

Experiment(s):

1. J-NSE: Neutron spin-echo spectrometer (NL2ao)

Appears in the scientific report 2012

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Database coverage:
; ; Allianz-Lizenz / DFG ; Current Contents - Social and Behavioral Sciences ; JCR ; NCBI Molecular Biology Database ; Nationallizenz ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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