Redox-responsive macroscopic gel assembly based on discrete dual interactions

Abstract

The macroscopic self-assembly of polymeric hydrogels modified with β-cyclodextrin (βCD gel), ferrocene (Fc gel), and styrenesulfonic acid sodium salt (SSNa gel) was investigated. Under reductive conditions, the Fc gel selectively adhered to the βCD gel through a host-guest interaction. On the other hand, the oxidized ferrocenium (Fc+) gel selectively adhered to the SSNa gel through an ionic interaction under oxidative conditions. The adhesion strength was estimated by a tensile test. We finally succeeded in forming an ABC-type macroscopic assembly of all three gels through two discrete noncovalent interactions. Changing partner on cue: The interaction between poly(acrylamide)-based hydrogels modified with β-cyclodextrin (βCD gel), ferrocene (Fc gel), and sodium p-styrenesulfonate (SSNa gel) was investigated. The βCD gel and the Fc gel selectively assembled with one another through a host-guest interaction (see picture). On the other hand, when Fc was oxidized to Fc+, the Fc+ gel selectively adhered to the SSNa gel through a cation-anion interaction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.