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Issue 7, 2010
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Polymer dynamics under soft confinement in a self-assembled system

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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.

Graphical abstract: Polymer dynamics under soft confinement in a self-assembled system

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Publication details

The article was received on 03 Nov 2009, accepted on 20 Jan 2010 and first published on 25 Feb 2010

Article type: Paper
DOI: 10.1039/B922649D
Citation: Soft Matter, 2010,6, 1559-1570
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    Polymer dynamics under soft confinement in a self-assembled system

    L. Willner, R. Lund, Michael. Monkenbusch, O. Holderer, J. Colmenero and D. Richter, Soft Matter, 2010, 6, 1559
    DOI: 10.1039/B922649D

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