Issue 11, 2009

Hole formation induced by ionic strength increase in exponentially growing multilayer films

Abstract

Polyelectrolyte multilayer (PEM) films consist of polyanion/polycation super-structures that are sensitive to various stresses like ionic strength changes. We investigate the swelling process of the exponentially growing poly(L-lysine)/hyaluronic acid (PLL/HA) films induced by changes of the ionic strength of the contact solution. We show that above a first critical ionic strength the swelling is accompanied by a release of both polyelectrolytes constituting the film, leading to its subsequent dissolution. At a second critical ionic strength, the swelling of the multilayer is so important that, in addition to this polyelectrolyte release, formation of spherical holes is observed inside the film. The presence of dissolved PLL and HA chains in these holes leads to an increase of the concentration of their counterions inside of them, and thus induces an extra osmotic pressure. This in turn favors the size increase of the holes before they coalesce. The release of both polyelectrolytes from the film into the supernatant ultimately allows a decrease of the osmotic pressure inside the PLL/HA film, which finally leads to the disappearance of the holes and concomitantly to a complete dissolution of the film. When the release of polyelectrolytes into the solution is prevented by a poly(diallyldimethyl ammonium chloride)/poly(styrene sulfonate) (PDADMAC/PSS) capping film, the holes appear at a smaller critical ionic strength compared to uncapped films. Here too the formation of the holes is attributed to an increase of the osmotic pressure inside the film. As soon as the capping barrier ruptures because of the swelling of the film, both PLL and HA chains can diffuse out of the film and the holes decrease in size and disappear, as does the film.

Graphical abstract: Hole formation induced by ionic strength increase in exponentially growing multilayer films

Supplementary files

Article information

Article type
Paper
Submitted
28 Oct 2008
Accepted
25 Mar 2009
First published
30 Apr 2009

Soft Matter, 2009,5, 2269-2276

Hole formation induced by ionic strength increase in exponentially growing multilayer films

H. Mjahed, J. Voegel, B. Senger, A. Chassepot, A. Rameau, V. Ball, P. Schaaf and F. Boulmedais, Soft Matter, 2009, 5, 2269 DOI: 10.1039/B819066F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements