Journal Article

PreJuSER-11980

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Polymer dynamics under soft confinement in a self-assembled system

Willner, L.FZJ* ; Lund, R. ; Monkenbusch, M.FZJ* ; Holderer, O.FZJ* ; Colmenero, J. ; Richter, D.FZJ*

2010
Royal Society of Chemistry (RSC) Cambridge

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Please use a persistent id in citations: doi:10.1039/B922649D

Abstract: Block copolymers that self-assemble into nano-structured melts provide an interesting template for soft confinement. An important question that arises is how the chain dynamics is affected in such self-assembled systems. Here we consider a system composed of poly(isoprene)-b-poly(dimethyl siloxane) (PI6-PDMS30, where the numbers indicate the molecular weight in kg mole(-1)) having a large asymmetry where the minor PI component block constitutes 19% of the total molecular weight. As shown by small angle neutron scattering (SANS), the system forms hexagonally ordered cylindrical structures composed of a PI phase (with a cylinder radius of about 6.4 nm) in a continuous PDMS matrix. Here we demonstrate using neutron spin-echo spectroscopy and careful H/D contrast matching schemes how the dynamics of single polymer chains (single chain contrast) and the interfacial dynamics of the domains can be resolved independently. This is achieved in the former "single chain contrast'' case by matching out the net domain scattering leaving only the intra chain coherent structure factor visible. In the latter "bulk contrast'' case, the protonated (h) PI and deuterated (d) PDMS domains are visible and most of the contrast comes from the small interfacial layer where h-PI/d-PDMS segments are intermixed and give rise to a significant contrast by which the fluctuations can be observed. Combining the results from the two contrast conditions, we show that the dynamics can be consistently described in terms of Rouse motion modified by the surface fluctuation and laterally restricted to 2D surface diffusion. Surprisingly, the fluctuations of the interface significantly contribute to the dynamics and the interfacial tension drives the fluctuations of a sizeable portion of the polymer chains while the dynamics is similar to Rouse motion.

Keyword(s): J

Note: The authors acknowledge the SoftComp Network of Excellence (NoE) program for support. The Basque Country Government (IT-436-07) and the Spanish Ministry of Education and Science (MAT 2007-63681) Consolider/Spanish Ministry of Education and Science are also gratefully acknowledged. We are also thankful to Dr Angel Moreno for many stimulating discussions and Dr Aurel Radulescu and Dr Marie-Sousai Appavou for assistance during the SANS experiments.

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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)

Experiment(s):

1. J-NSE: Neutron spin-echo spectrometer (NL2ao)
2. KWS-2: Small angle scattering diffractometer (NL3ao)

Appears in the scientific report 2010

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