Charge trapping by anionic quinones electrostatically bound to a highly charged cationic quinone-viologen polymer or a cationic poly(3-viologen-thiophene)

Charge associated with quinone reduction is trapped at low pH in systems composed of sulfonated anthraquinones electrostatically bound to a polymer derived from a monomer consisting of a quinone unit flanked by two viologen units. Each monomer repeat unit carries 6 equiv of positive charge which can be charge compensated by monosulfonated anthraquinone to yield a quinone:viologen ratio of nearly 7:2. At low pH, electrostatic binding is persistent, and the amount of trapped charge is 90% of the theoretical maximum. Some of the electrostatically bound quinone can be replaced with Fe(CN)₆^3- to allow mediated release of trapped charge via the Fe(CN)₆^3-/4- redox couple. I^- is blocked from entering the polymer and thus does not mediate release of charge. Electrostatic binding of anionic quinones to a thiophene polymer with pendant viologen units has also been demonstrated. This polymer system has the unique property of having built-in mediators for both the reduction (charge trapping) and oxidation (charge release) of the electrostatically bound anthraquinone.