Issue 22, 2016

Double-network hydrogels improve pH-switchable adhesion


For environmentally-switchable adhesive systems to be reused repeatedly, the adhesive strength must not deteriorate after each adhesion cycle. An important criterion to achieve this goal is that the integrity of the interface must be retained after each adhesion cycle. Furthermore, in order to have practical benefits, reversing the adhesion must be a relatively rapid process. Here, a double-network hydrogel of poly(methacrylic acid) and poly[oligo(ethylene glycol)methyl ether methacrylate] is shown to undergo adhesive failure during pH-switchable adhesion with a grafted (brush) layer of polycationic poly[2-(diethyl amino)ethyl methacrylate], and can be reused at least seven times. The surfaces are attached at pH 6 and detached at pH 1. A single-network hydrogel of poly(methacrylic acid), also exhibits pH-switchable adhesion with poly[2-(diethyl amino)ethyl methacrylate] but cohesive failure leads to an accumulation of the hydrogel on the brush surface and the hydrogel can only be reused at different parts of that surface. Even without an environmental stimulus (i.e. attaching and detaching at pH 6), the double-network hydrogel can be used up to three times at the same point on the brush surface. The single-network hydrogel cannot be reused under such circumstances. Finally, the time taken for the reuse of the double-network hydrogel is relatively rapid, taking no more than an hour to reverse the adhesion.

Graphical abstract: Double-network hydrogels improve pH-switchable adhesion

Supplementary files

Article information

Article type
16 Mar 2016
03 May 2016
First published
10 May 2016
This article is Open Access
Creative Commons BY license

Soft Matter, 2016,12, 5022-5028

Author version available

Double-network hydrogels improve pH-switchable adhesion

L. Alfhaid, W. D. Seddon, N. H. Williams and M. Geoghegan, Soft Matter, 2016, 12, 5022 DOI: 10.1039/C6SM00656F

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