This work reports the synthesis of novel poly(3,4-bis(alkyloxy)terthiophene) derivatives (PTTOBu, PTTOHex, and PTTOOct) and their supercapacitor applications as redox-active electrodes. The terthiophene-based conducting polymers have been derivatized with different alkyl pendant groups (butyl-, hexyl-, and octyl-) to explore the effect of alkyl chain length on the surface morphologies and pseudocapacitive properties. The electrochemical performance tests have revealed that the length of alkyl substituent created a remarkable impact over the surface morphologies and charge storage properties of polymer electrodes. PTTOBu, PTTOHex, and PTTOOct-based electrodes have reached up to specific capacitances of 94.3, 227.3, and 443 Fg(-1) at 2.5 mAcm(-2) constant current density, respectively, in a three-electrode configuration. Besides, these redox-active electrodes have delivered satisfactory energy densities of 13.5, 29.3, and 60.7 Whkg(-1) and power densities of 0.98, 1, and 1.1 kWkg(-1) with good capacitance retentions after 10,000 charge/discharge cycles in symmetric solid-state micro-supercapacitor devices. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 480-495