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Adsorption of polyelectrolytes onto the oppositely charged surface of tubular J-aggregates of a cyanine dye

Authors
  • Al-Khatib, Omar1, 2
  • Böttcher, Christoph3
  • von Berlepsch, Hans3
  • Herman, Katherine1
  • Schön, Sebastian4
  • Rabe, Jürgen P.1, 2
  • Kirstein, Stefan1
  • 1 Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr 15, Berlin, 12489, Germany , Berlin (Germany)
  • 2 IRIS Adlershof, Humboldt-Universität zu Berlin, Zum Großen Windkanal 6, Berlin, 12489, Germany , Berlin (Germany)
  • 3 Freie Universität Berlin, Research Center of Electron Microscopy, Fabeckstr 36a, Berlin, 14195, Germany , Berlin (Germany)
  • 4 Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, Berlin, 10623, Germany , Berlin (Germany)
Type
Published Article
Journal
Colloid & Polymer Science
Publisher
Springer-Verlag
Publication Date
Mar 12, 2019
Volume
297
Issue
5
Pages
729–739
Identifiers
DOI: 10.1007/s00396-019-04487-5
Source
Springer Nature
Keywords
License
Yellow

Abstract

The adsorption of three different polycations at the negatively charged surface of tubular J-aggregates of the amphiphilic cyanine dye 3,3′-bis(2-sulfopropyl)-5,5′,6,6′-tetrachloro-1,1′-dioctylbenzimidacarbocyanine (C8S3) is investigated by means of cryogenic electron microscopy and optical absorption spectroscopy. All three polycations could be adsorbed at the tubular aggregates without flocculation or precipitation when added in molar amounts of monomers sufficiently smaller than that of the dye molecules. It is found that preferably, a minority of aggregates is coated by the polycations while a majority of aggregates is left uncoated. For the coated aggregates, the adsorption leads to charge reversal of the aggregate surface as supported by zeta potential measurements. The morphology of the coating differs significantly for the three polycations: The branched polycation polyethylenimine (PEI) attaches to the tubular aggregate by hit-and-stick adsorption of the coiled state in solution forming irregular clot-like coatings; the flexible and weakly cationic poly (allylamine hydrochloride) (PAH) forms a more homogeneous coating but destroys the integrity of the dye aggregate; the more hydrophobic and strong polycation poly (diallyldimethylammonium chloride) (PDADMAC) forms a thin and homogeneous layer, supposedly by wrapping around the tubular aggregate. For the latter growth of a second double layer of dyes is observed for the aggregates. The different morphologies of the coating layers are explained by the details of the chemical structure of the polycations. The possible adsorption of polyelectrolytes at these amphiphilic tubular structures, stabilized by means of hydrophobic forces, is far from obvious and demonstrates an applicable route to the build-up of more complex nanostructures in solution by means of a self-assembly process.

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