Macroscopically Aligned Ionic Self-Assembled Perylene-Surfactant Complexes within a Polymer Matrix

Authors

  • Ari Laiho,

    1. Department of Engineering Physics and Center for New Materials Helsinki University of Technology P.O. Box 5100, 02015 TKK, Espoo (Finland)
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  • Bernd M. Smarsly,

    1. Physikalisch-Chemisches Institut Justus Liebig Universität Gießen Heinrich Buff Ring 58, 35392 Gießen (Germany)
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  • Charl F. J. Faul,

    Corresponding author
    1. School of Chemistry, University of Bristol Bristol BS8 1TS (UK)
    • School of Chemistry, University of Bristol Bristol BS8 1TS (UK).
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  • Olli Ikkala

    Corresponding author
    1. Department of Engineering Physics and Center for New Materials Helsinki University of Technology P.O. Box 5100, 02015 TKK, Espoo (Finland)
    • Department of Engineering Physics and Center for New Materials Helsinki University of Technology P.O. Box 5100, 02015 TKK, Espoo (Finland).
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  • We thank Dr. Laszlo Almasy (Helsinki University of Technology) for useful discussions. This work has been supported as part of the European Science Foundation Collaborative Research (EUROCORES) Programme on Self-Organised NanoStructures (SONS). The University of Bristol, MPG and the Academy of Finland are acknowledged. The work was partly carried out in the Centre of Excellence of Finnish Academy (Bio- and Nanopolymers Research Group, 77317). C.F.J.F. thanks HUT for a visiting professorship.

Abstract

Ionic self-assembled (ISA) surfactant complexes present a facile concept for self-assembly of various functional materials. However, no general scheme has been shown to allow their overall alignment beyond local polydomain-like order. Here we demonstrate that ionic complexes forming a columnar liquid-crystalline phase in bulk can be aligned within polymer blends upon shearing, taken that the matrix polymers have sufficiently high molecular weight. We use an ISA complex of N,N′-bis(ethylenetrimethylammonium)perylenediimide/bis(2-ethylhexyl) phosphate (Pery-BEHP) blended with different molecular weight polystyrenes (PS). Based on X-ray scattering studies and transmission electron microscopy the pure Pery-BEHP complex was found to form a two-dimensional oblique columnar phase where the perylene units stack within the columns. Blending the complex with PS lead to high aspect ratio Pery-BEHP aggregates with lateral dimension in the mesoscale, having internal columnar liquid-crystalline order similar to the pure Pery-BEHP complex. When the Pery-BEHP/PS blend was subjected to a shear flow field, the alignment of perylenes can be achieved but requires sufficiently high molecular weight of the polystyrene matrix. The concept also suggests a simple route for macroscopically aligned nanocomposites with conjugated columnar liquid-crystalline functional additives.

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