Electrolyte-controlled redox conductivity and n-type doping in poly(bis-EDOT-pyridine)s

We report the use of electrolyte variations as a means to actively control redox and n-type doping processes in π-conjugated electroactive polyheterocycles. Specifically, a series of donor−acceptor bis-EDOT-pyridine polymers, poly[2,5-bis-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-pyridine] (PBEDOT-Pyr) and poly[5,8-bis(3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-2,3-diphenyl-pyrido[3,4-b]pyrazine (PBEDOT-PyrPyr(Ph)2), have been investigated. The use of soft, bulky cations, such as n-alkylammonium, allows true n-type doping to be observed in cyclic voltammetry, differential-pulse voltammetry, and in situ conductance experiments. Color changes are also observed upon conversion of the polymers from their neutral to reduced states. Hard, electrophilic cations, such as lithium and sodium, induce minimal current and conductivity responses for these polymeric systems. This “pinning” of the cation−anion pair causes a decrease in the electrochemical and conductivity response. Optical changes upon reduction are obse...