Synthesis and electrochromic performances of donor-acceptor-type polymers from chalcogenodiazolo [3,4-c]pyridine and alkyl ProDOTs

Abstract

Chalcogenodiazolo [3,4-c]pyridine, an important analogue of benzothiadiazole (BT), have stronger electron-accepting nature and unique electrochemistry and electrochromic advantages over BT in the NIR region, inspiring us to explore chalcogenodiazolo [3,4-c]pyridine-based donor-acceptor-type (D-A) conjugated polymers. Herein, a series of chalcogenodiazolo [3,4-c]pyridine and alkyl substituted 3,4-propylenedioxythiophenes (ProDOTs) bearing D-A-type conjugated precursors were synthesized by Stille coupling, and electropolymerized to yield the corresponding polymers. The electrochemistry behavior and electrochromic properties of the polymers were comparatively investigated by cyclic voltammetry (CV) and spectroelectrochemistry in detail. All the precursors revealed strong orange/purple/pink/bluish violet light emission with fluorescence quantum yields ranging from 0.09 to 0.60. Electrochromic results demonstrated that chalcogenodiazolo [3,4-c]pyridine-ProDOTs polymers revealed relatively good transmittance changes (ΔT%) of 38%, high coloration efficiency of 370 cm2 C−1 in the near-infrared (NIR) region and excellent switching stability (less than 4% after 2000 cycles). In comparison with polymers from chalcogenodiazolo [3,4-c]pyridine and thiophene, 3-alkylthiophene and EDOT, these polymers displayed higher coloration efficiency and better stability, resulting from the introduction of ProDOTs donor units. From these results, chalcogenodiazolo [3,4-c]pyridine-ProDOTs can be further explored as green and NIR electrochromic materials towards indoor electrochromic products and flexible displays.