Electroactive Microgel Systems

The principles of electrochemical switching of polymers are discussed in the light of redox-active microgel systems, which could contribute to efficient energy storage or sensing. First, the preparation of electroactive microgels is addressed, highlighting some of the most engaged electroactive moieties used in polymer science. Examples are given, where the swelling/collapse of microgels can be induced by electrochemical means and/or where the thermo-induced collapse leads to switchable electroactivity. The charge transport to/from and within microgels is discussed, pointing also to open questions of electrochemistry with electroactive colloids. While e-microgels adsorbed to electrodes can have similar electrochemical characteristics to thin electroactive hydrogel films, the electrochemical scenario of microgels dispersed in solution is more complex. In sum, microgels with strongly linked electroactive units, microgels with specific interactions to otherwise freely diffusing electroactive species (complexants), and microgels with electroactive species produced directly within the microgel (often by enzymes) are presented.