Optical and electrochemical properties of regiosymmetric and soluble alkylenedioxyselenophene-based electrochromic polymers, namely poly(3,3-dibutyl-3,4-dihydro-2H-seleno pheno [3,4-b][1,4]dioxephine) (PProDOS-C(4)), poly(3,3-dihexyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxephine) (PProDOS-C(6)), and poly(3,3-didecyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxephine) (PProDOS-C(10)), are highlighted. It is noted that these unique polymers have low bandgaps (1.57-1.65 eV), and they are exceptionally stable under ambient atmospheric conditions. Polymer films retained 82-97% of their electroactivity after 5000 cycles. The percent transmittance of PProDOS-C(n) (n = 4, 6, 10) films found to be between 55 and 59%. Furthermore, these novel soluble PPro-DOS-C(n) polymers showed electrochromic behavior: a color change form pure blue to highly transparent state in a low switching time (1.0 s) during oxidation with high coloration efficiencies (328-864 cm(2) C(-1)) when compared to their thiophene analogues. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4398-4405, 2011