A new processable donor–acceptor polymer displaying neutral state yellow electrochromism

We report here the synthesis of a new solution processable neutral state yellow polymeric electrochromic material containing 2,5-bis-dithienyl-1H-pyrrole (SNS)-donor and 1,8 naphthalimide-acceptor (SNS–NI) as a subunit. The electrochemical and optical properties were investigated via cyclic voltammetry (CV), UV–Vis absorption and fluorescence emission measurements, respectively. Besides, electrochromic performance of poly(SNS–NI) has been compared to the both the film preparation method and poly(1-phenyl-2,5-dithiophen-2-ylpyrrole) [poly(SNS–P)] as a standard polymer. In the poly(SNS–NI), yellow color of the polymer film at neutral state converted to green and then dark blue upon the polymer film fully oxidized in the positive regime. SNS–NI polymer film prepared via spin casting process exhibits a high contrast ratio in the near-IR region (ΔT% = 56% at 890 nm), a response time of about 1 s, high coloration efficiency (299 cm2 C−1) and retained its performance by 98.6% even after 5000 cycles. Finally, the results clearly indicate that both electronic nature of the molecule and film preparation method have a major impact on electrochromic performance of these polymers.