Multicolored Electrochromic Cells Based On Poly(2,7-Carbazole) Derivatives For Adaptive Camouflage

We report the synthesis and characterization of three new poly(2,7-carbazole) derivatives, namely, poly [N-9-heptadecanyl-2,7-carbazole-alt-5,7-di(3-octylthien-2-yl)-2,3-di(thien-3-yl)-thieno[3,4-b]pyrazine (P1), poly [N-9-heptadecanyl-2,7-carbazole-alt-5,7-di (3-octylthien-2-yl)-2,3-di(phen-1-yl)-thieno[3,4-b]pyrazine (P2), and poly [N-9-heptadecanyl-2,7-carbazole-alt-5,7-di(3-octylthien-2-yl)-2,3di(4-octylphen-1-yl)-thieno[3,4-b]pyrazine (P3), which reflect green light in their neutral state and show transmissive brown when oxidized. These two colors are compatible for adaptive camouflage for military assets. All solid-state electrochromic cells were prepared using spray-coated films of electrochromic conjugated polymer (P1-P3) as active layer. We report the development of multicolored electrochromic cells (MEC) based on the additive color mixing theory. MEC of various sizes were prepared from 2.5 x 2.5 cm, and up to 12.5 x 12.5 cm. Finally, we also describe the fabrication of a multicolored electrochromic cell with an active surface of 156 cm(2).