posted on 2024-03-12, 13:35authored byMarlow
M. Durbin, Alex H. Balzer, John R. Reynolds, Erin L. Ratcliff, Natalie Stingelin, Anna M. Österholm
Mixed ionic/electronic conducting polymers are versatile
systems
for, e.g., energy storage, heat management (exploiting electrochromism),
and biosensing, all of which require electrochemical doping, i.e.,
the electrochemical oxidation or reduction of their macromolecular
backbones. Electrochemical doping is achieved via electro-injection
of charges (i.e., electronic carriers), stabilized via migration of
counterions from a supporting electrolyte. Since the choice of the
polymer side-chain functionalization influences electrolyte and/or
ion sorption and desorption, it in turn affects redox properties,
and, thus, electrochemically induced mixed conduction. However, our
understanding of how side-chain versus backbone design can increase
ion flow while retaining high electronic transport remains limited.
Hence, heuristic design approaches have typically been followed. Herein,
we consider the redox and swelling behavior of three poly(propylenedioxythiophene)
derivatives, P(ProDOT)s, substituted with different side-chain motifs,
and demonstrate that passive swelling is controlled by the surface
polarity of P(ProDOT) films. In contrast, active swelling under operando
conditions (i.e., under an applied bias) is dictated by the local
side-chain free volume on the length scale of a monomer unit. Such
insights deliver important design criteria toward durable soft electrochemical
systems for diverse energy and biosensing platforms and new understanding
into electrochemical conditioning (“break-in”) in many
conducting polymers.