Optical and electrochromic characterizations of four 2,5-dithienylpyrrole-based conducting polymer films

Hexyloxy-phenyl (C6OP), hexyl-phenyl (HexP), isopropylphenyl (iProP), and 3,4-dimethylphenyl (3,4dMP) groups were introduced into the pyrrole ring of dithienylpyrrole-based conducting polymers backbone. The four conjugated polymers were synthesized using electrochemical polymerization and were used as electrochromic materials to study the effects of units of substitution on the electrochromic properties in various supporting electrolytes. Spectroelectrochemical studies demonstrated that the four poly(2,5-dithienylpyrrole) derivatives (PSNS) could be reversibly oxidized and reduced, with accompanying obvious color changed from yellow to blue. The maximum contrast (ΔT%) of the PSNS-C6OP film was measured as 28.4% in TBAClO4-based supporting electrolyte, and the maximum coloration efficiency (η) of the PSNS-HexP film was calculated to be 204.2 cm2 C−1 in TBABF4-based supporting electrolyte. Electrochromic switching studies showed that PSNS-iProP was faster to change color from the dedoped to the doped state than were PSNS-C6OP, PSNS-HexP, and PSNS-3,4dMP.