Facilely Tunable Redox Behaviors in Donor-Node-Acceptor Polymers toward High-Performance Ambipolar Electrode Materials

Conjugation breaking by node structures in donor-node-acceptor (D-n-A)-type molecules conceptually enables facile tuning of their oxidation and reduction behaviors through modification of the donor (D) unit and the acceptor (A) unit independently. Herein, we demonstrate the successful synthesis of a series of D-n-A-type cross-linked polymers, termed poly-4T-PDI, poly-2T(3)-PDI, and poly-4T(3)-PDI, by an in situ electrochemical polymerization reaction on the surface of electrodes and their versatile redox properties. These polymers contain oligo-thiophene structures connected with tetrachloronated perylene diimide (PDI) units through the N node. The investigation of the redox behaviors of these three polymers clearly indicates that there are two reversible redox waves corresponding to the oxidation-reduction couples of PDI/PDI- and PDI-/PDI2-; however, the redox signal relating to the oligo-thiophene structures completely relies on the number and connection mode of thiophene units. Especially, poly-2T(3)-PDI possesses a balanced ambipolar characteristic showing approximately equivalent gravimetric capacitances of 299 F g(-1) for the n-doping process and 264 F g(-1) for the p-doping process, which facilitate the application of such ambipolar polymers as both cathode and anode materials in pseudocapacitors. In addition, electrochemical impedance spectroscopy indicates easy ion diffusion and fast electron transfer in the film of poly-2T(3)-PDI, which is attributed to the fine porous structure and the conjugated backbone of polythiophene. The current research clearly demonstrates a facile strategy to achieve balanced ambipolar polymers through conjugation breaking by the node structure between the electron donor and acceptor units.

Automated summary

Conjugation breaking by node structures in D-n-A-type molecules allows for facile tuning of oxidation and reduction behaviors. Electrochemical polymerization on electrodes produces a series of cross-linked polymers with versatile redox properties. One polymer, poly-2T(3)-PDI, shows balanced ambipolar characteristics and potential for application in pseudocapacitors.