Capacitive studies of electrodeposited PEDOT-maleimide

Abstract

Here we examined the capacitive behavior of electrodeposited poly(2′-maleimideomethyl-3,4-ethylenedioxythiophene) (PEDOT-maleimide) and compared it to poly(3,4-ethylenedioxythiophene) (PEDOT). According to results of linear cyclic voltammetry (linear CV) and galvanostatic charging/discharging (GCD) in 0.1 M KCl aqueous solution, PEDOT-maleimide presented higher areal specific capacitance, 5.8 × 10⁻³ F cm⁻² at 25 mV s⁻¹ and 7.0 × 10⁻³ F cm⁻² at 1.6 × 10⁻⁴ A cm⁻², while PEDOT exhibited 5.4 × 10⁻³ F cm⁻² at 25 mV s⁻¹ and 6.3 × 10⁻³ F cm⁻² at 1.6 × 10⁻⁴ A cm⁻². Improved cyclic stability of the PEDOT-maleimide was also achieved which correlated with better mechanical properties as revealed by nanoindentation. The effective Young's modulus for PEDOT-maleimide was 4.5 GPa, while it was 1.8 GPa for PEDOT. Roughness studies on surface topographies, determined by atomic force microscopy (AFM) and analyzed by power spectral density (PSD) and root-mean-square (RMS) roughness, revealed that PEDOT-maleimide was rougher than PEDOT at small length scales (below ∼1 μm) but smoother at large length scales (above ∼1 μm), which was also consistent with complementary observations by scanning electron microscopy (SEM). PEDOT-maleimide showed decreased scattering from the side-to-side (lamellar stacking) ∼1.21 nm and ∼0.34 nm face-to-face (π–π stacking) signals as confirmed by grazing-incidence wide-angle X-ray scattering (GIWAXS). This change directly made PEDOT-maleimide less conductive than PEDOT, 0.58 vs. 3.34 S cm⁻¹. However, the impedance performance across a broad range of frequencies (10⁻¹ to 10⁵ Hz) was similar for both PEDOT and PEDOT-maleimide, indicating that both materials remained effective at charge transport. Those results indicate that PEDOT-maleimide is a promising alternative to PEDOT for charge storage applications.