Microgels are crosslinked polymeric particles consisting of a porous network swollen by a solvent with the ability to undergo often a volume phase transition with respect to environmental changes. Introduction of charges into the microgel network leads to a possible interaction of the polyelectrolyte microgel with oppositely charged counterions based on electrostatic attraction (host-guest interplay). The charge of guest molecules can be changed by various means. Besides light-sensitive counterions,[1] electrochemically-addressable counterions are of scientific interest since years. For example, electrolysis of complexes between linear polyelectrolytes and hexacyanoferrates leads to a film formation onto the electrodes,[2] while the polymer architecture has an influence on these processes. We could demonstrate recently an electrochemically-triggered bulk aggregation of branched macromolecules in combination with redox-active species and simultaneous switching between the unimeric and the micellar/vesicular state.[3] We now address thermoresponsive cationic microgels and their influence on the electrochemistry of hexacyanoferrates. Further, we investigate the influence of the counterion guests on the swelling of the microgel hosts. The combination of hydrodynamic voltammetry and electrochemical impedance spectroscopy allowed a distinction between the electron pathways.[4] In addition, the data strongly suggest the selective uptake of ferricyanide and an encapsulation of the guest molecules inside the microgel network at elevated temperatures. By that, the size of the cationic microgel can be reversibly modulated by electrochemical switching leading to a redox-responsive microgel system.[5] In addition, there is an increased contribution of direct electron injection into the [Fe(CN)6]3--microgel complex, as seen by impedance spectroscopy. References: [1] F.A.Plamper, J.R.McKee, A.Laukkanen, A.Nykänen, A.Walther, J.Ruokolainen, V.Aseyev, H.Tenhu, Soft Matter 2009, 5, 1812. [2] M.Ohyanagi, F.C.Anson, J. Phys. Chem. 1989, 93, 8377. [3] F.A.Plamper, L.Murtomäki, A.Walther, K.Kontturi, H.Tenhu, Macromolecules 2009, 42, 7254. [4] F.A.Plamper, Adv. Polym. Sci. 2014, DOI: 10.1007/122014284. [4] O.Mergel, A.P.H.Gelissen, P.Wünnemann, A.Böker, U.Simon, F.A.Plamper; J. Phys. Chem. C, 2014, 118, 26199. [5] O.Mergel, P.Wünnemann, A.Böker, U.Simon, F.A.Plamper; Mater. Chem., 2015, DOI:10.1021/acs.chemmater.5b02740

Electrochemically-triggered microgel size modulation

251st National Meeting (2016)

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