Binary-encoded conjugated polythiophenes with alternating carbon–carbon single and triple bonds for tunable electrochromic and energy storage applications

Abstract

Two binary-encoded conjugated polymers, PCT2T and PCT3T, were synthesized through electrochemical polymerization of their corresponding monomers, incorporating carbon-carbon single and triple bonds as bridging linkers. These polymers exhibit unique electrochromic and energy storage properties Upon electrochemical doping, PCT2T displays a maximum optical contrast of 42 % at 750 nm, while PCT3T exhibits a superior optical contrast of 57 %. The coloration efficiency of PCT2T is 207.16 cm²/C, while PCT3T achieves a higher value of 330.9 cm²/C. By introducing carbon-carbon triple bonds at the 2,5 positions of a fully single-bonded polythiophene structure, a blue shift in the cationic radical state can be achieved. Moreover, increasing the number of carbon-carbon triple bonds leads to a red shift in the oxidation state spectrum. In the electrochemical performance evaluation, PCT2T demonstrated an areal specific capacitance of 1.81 mF/cm² at a current density of 0.04 mA/cm². Similarly, PCT3T exhibited a higher areal specific capacitance of 2.17 mF/cm² under the same current density. This performance suggests that the incorporation of triple bonds significantly affects the electronic and optical properties of the material, providing an effective strategy to fine-tune its electrochromic energy storage behaviors.