Benzyl substituted benzotriazole containing conjugated polymers: Effect of position of the substituent on electrochromic properties

New classes of EDOT coupled-benzotriazole bearing π-conjugated monomers containing benzyl units on electron-withdrawing benzotriazole moiety were synthesized. The effect of structural differences on electrochemical and optoelectronic properties of the resulting polymers (PBBTES and PBBTEA) was investigated. The results showed that the insertion of benzyl substituent to benzotriazole from different positions changes the electronic structure of polymer which results in completely different electrochemical and optical properties. PBBTES has a very low oxidation potential (0.13 V) compared to the oxidation potential of PBBTEA (0.98 V). Spectroelectrochemical analyses revealed that PBBTES is blue in its neutral state with a π–π* transition at 625 nm whereas PBBTEA is orange in its neutral state with a π–π* transition at 477 nm. The band gap (Eg) values for PBBTES and PBBTEA were calculated as 1.48 eV and 1.57 eV, respectively. PBBTEA can be switched between blue neutral state and light blue oxidized state while PBBTEA reveals orange color at the neutral state and gray color at oxidized state.