Prof. Schubert Group - Redox Polymers

Redox polymers have been the subject of an intense research activity due to its promising electrical property as an active material for organic electronics such as organic solar cells, organic light-emitting diodes, sensors and organic electrical charge-storage devices. Redox polymers are characterized by the presence of electrostatically and spatially localized redox sites which can be oxidized or reduced.

Recently the group of Prof. Schubert reported the synthesis of novel redox-active polymer containing π-extended tetrathiafulvalenes systems and its application in a Li-organic battery¹. A novel redox-active polymer, poly(2-vinyl(exTTF)), was synthesized from 2-vinyl(exTTF) (V0136) using the free radical polymerization technique with 2,2′-azobis(2-methylpropionitrile) (AIBN) as initiator (Scheme 1). The chemical properties of poly(2-vinyl(exTTF) can be influenced by the choice of the appropriate solvent and the amount of initiator. Due to the low solubility of 2-vinyl(exTTF) (V0136), the polymerization was best performed in DMSO, leading to high conversions, polymers with high molar mass (M_n = 6.02 × 10³ g mol ⁻¹), and a narrow molar mass distribution (PDI = 2.04). Poly(2-vinyl(exTTF)) is soluble in N,N′-dimethylformamide (DMF), N,N′-dimethylacetamide (DMAc), and dimethylsulfoxide (DMSO), as well as insoluble but swellable in common electrolytes.

Poly(2-vinyl(exTTF)) undergoes a redox reaction involving two electrons to form dicationic species in a single step. During the oxidation, the release of the second electron is promoted due to the planar low-energy conformation associated with the re-aromatization of the oxidized dicationic product. Cyclic voltammetry of monomer (V0136) in acetonitrile solution reveals an electrochemical response at ( E_pa + E_pc ) / 2 = −0.2 V vs Fc / Fc⁺. The exTTF units have proven to be a promising core structure as an active material unit for organic batteries. The application of poly(2-vinyl(exTTF)) in a Li-organic battery enables charge-storage devices that display a theoretical capacity of 132 mAh g⁻¹, together with a constant cell potential and a long lifetime exceeding 250 cycles.