Supramolecular assembly of water-soluble poly(ferrocenylsilanes): multilayer structures on flat interfaces and permeability of microcapsules

Yujie Ma; Wen-Fei Dong; E. Stefan Kooij; Mark. A. Hempenius; Helmuth Möhwald; G. Julius Vancso

doi:10.1039/B702132A

Supramolecular assembly of water-soluble poly(ferrocenylsilanes): multilayer structures on flat interfaces and permeability of microcapsules

Yujie Ma,^a Wen-Fei Dong,^bc E. Stefan Kooij,^d Mark. A. Hempenius,^a Helmuth Möhwald^c and G. Julius Vancso*^a

* Corresponding authors

^a Department of Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands
E-mail: g.j.vancso@tnw.utwente.nl
Fax: +31 53 4893823
Tel: +31 53 4892974

^b Department of Materials Engineering, Graduate School of Engineering and Center for NanoBio Integration, The University of Tokyo, Tokyo, Japan

^c Max Planck Institute of Colloids and Interfaces, Golm, Potsdam, D-14476, Germany

^d Department of Solid State Physics, MESA+ Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands

Abstract

We report on the layer-by-layer (LBL) supramolecular assembly of redox responsive, organometallic polyion films on planar and curved (spherical) substrates. Organometallic poly(ferrocenylsilane) (PFS) polyanions and polycations were first used to assemble multilayers on planar quartz, silicon and quartz-crystal microbalance (QCM) electrodes. UV/Vis spectroscopy, spectroscopic ellipsometry and quartz-crystal microgravimetry showed a linear increase of UV absorbance, film thickness and frequency shift with increasing the number of deposited bilayers. Additional ellipsometric studies showed a square-root dependence of the film thickness on solution salt (NaCl) concentration. For the preparation of multilayer films on colloidal particles (manganese carbonate, MnCO₃), relatively high salt concentrations (0.5 M) were employed. PFS microcapsules were subsequently obtained by colloidal template removal using ethylenediaminetetraacetic acid (EDTA). Following the removal of the spherical template, hollow microcapsules were obtained, whose wall structure–permeability characteristics received particular attention. Atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM) were used to study the wall thickness, integrity and permeability of the capsules. Capsule-wall thickness obtained from AFM indicated the existence of a linear film growth regime when the number of adsorbed bilayers was larger than four. Capsules made of PFS polyanions and rhodamine-labelled PFS polycations were directly visualized by CLSM. Using tetramethylrhodamine isothiocyanate (TRITC)-labelled dextran (M_w ∼ 4 400 g mol⁻¹) as probe, CLSM showed that capsules containing more than four PFS polycation–polyanion bilayers displayed good stability and integrity. These stable capsules are excellent candidates for the investigation of polyelectrolyte microcapsule permeability control triggered by redox stimuli.

Soft Matter

Supramolecular assembly of water-soluble poly(ferrocenylsilanes): multilayer structures on flat interfaces and permeability of microcapsules

Abstract

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Supramolecular assembly of water-soluble poly(ferrocenylsilanes): multilayer structures on flat interfaces and permeability of microcapsules

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