Chapter 4.4. Stimuli-Responsive Capsules

  1. Dr. Renate Förch3,
  2. Prof. Dr. Holger Schönherr4 and
  3. Dr. A. Tobias A. Jenkins5
  1. Yujie Ma1,
  2. Mark A. Hempenius1,
  3. E. Stefan Kooij1,
  4. Wen-Fei Dong2,
  5. Helmuth Möhwald2 and
  6. G. Julius Vancso1

Published Online: 9 SEP 2009

DOI: 10.1002/9783527628599.ch18

Surface Design: Applications in Bioscience and Nanotechnology

Surface Design: Applications in Bioscience and Nanotechnology

How to Cite

Ma, Y., Hempenius, M. A., Kooij, E. S., Dong, W.-F., Möhwald, H. and Vancso, G. J. (2009) Stimuli-Responsive Capsules, in Surface Design: Applications in Bioscience and Nanotechnology (eds R. Förch, H. Schönherr and A. T. A. Jenkins), Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany. doi: 10.1002/9783527628599.ch18

Editor Information

  1. 3

    Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

  2. 4

    University of Siegen, Department of Physical Chemistry, Adolf-Reichwein-Straße 2, 57076 Siegen, Germany

  3. 5

    University of Bath, Department of Chemistry, Bath BA2 7AY, United Kingdom

Author Information

  1. 1

    University of Twente, MESA+ Institute for Nanotechnology, Department of Materials Science and Technology of Polymers, P.O. Box 217, 7500 AE Enschede, The Netherlands

  2. 2

    Max-Planck-Institute of Colloids and Interfaces, 14476 Golm/Potsdam, Germany

Publication History

  1. Published Online: 9 SEP 2009
  2. Published Print: 12 JUN 2009

ISBN Information

Print ISBN: 9783527407897

Online ISBN: 9783527628599

SEARCH

Keywords:

  • stimuli-responsive capsules;
  • multilayer fabrication;
  • polyelectrolyte multilayer capsule preparation;
  • redox characteristics of PFS multilayers;
  • microcapsule formation;
  • permeability threshold

Summary

Poly(ferrocenylsilane) (PFS) polyanions and polycations have been successfully employed in a electrostatic layer-by-layer supramolecular self-assembly process to form fully organometallic multilayer architectures. The presence of redox-active ferrocene units in the polyelectrolyte main chain offers fast-response characteristics of these multilayer structures to external redox stimuli. Planar PFS multilayers disassemble upon exposure to oxidants such as ferric chloride (FeCl3), as was shown by UV/Vis spectroscopy and ellipsometry measurements. Microcapsules made of PFS polyion pairs showed increased permeability in response to oxidation by FeCl3 according to confocal laser scanning microscopy (CLSM) measurements, using tetramethylrhodamine isothiocyanate (TRITC) labeled dextran (4400 g/mol) as a fluorescence probe. The permeability increase was accompanied by a continuous expansion of the PFS-/PFS+ microcapsules until their final disintegration. Capsule expansion could be suppressed by the addition of the reducing agent dithiothreitol (DTT). The mechanism of the responsive permeability and expansion behavior of PFS-/PFS+ capsules was clarified in a systematic study of the oxidation of microcapsules based solely on PFS polyelectrolytes (PFS-/PFS+), as well as on capsules made of one PFS polyion component and one redox-insensitive polyelectrolyte species. For these heterostructured capsules, poly(styrene sulfonate) (PFS+/PSS-) and poly(allylamine hydrochloride) (PFS-/PAH+) were chosen. Composite-wall microcapsules composed of PFS-/PFS+ polyions in the inner wall and redox-insensitive polyelectrolyte species of PSS- and PAH+ on the outer wall were fabricated and studied. The introduction of the composite-wall capsule structure was shown to not only overcome the stability issue related to the uncontrolled expansion of PFS-/PFS+ capsules, but also offers a broad scope for manipulating the speed of the characteristic permeability response. The well-preserved redox characteristics of these composite-wall microcapsules were further confirmed via electrochemical experiments (cyclic voltammetry, CV), by depositing them onto sodium 3-mercapto-1-propanesulfonate modified gold substrates. The redox-responsive permeability of the organometallic capsules may lead to new applications in the expanding areas of controlled release, smart encapsulation, anticorrosive and self-healing coatings.