Synthesis and electrochromic properties of a new family of methacrylate polymers containing pendant oligothiophenes

A new family of methacrylate polymers containing pendant terthiophene, quaterthiophene, quinquethiophene, and sexithiophene was synthesized by the radical polymerization of the corresponding methacrylate monomers, and the electrochemical and electrochromic properties were investigated. The anodic oxidation of these polymers in the presence of tetra‐ n ‐butylammonium perchlorate as a supporting electrolyte produced radical‐cation salts of pendant oligothiophenes with ClO as a dopant. The electrochemically oxidized polymers had partially crosslinked structures resulting from the coupling reaction of pendant oligothiophene radical cations, the extent of crosslinking significantly decreasing with the increasing conjugation length of the pendant oligothiophenes. Comparative spectroelectrochemical studies of the monomers in solution and the polymers as solid films showed that π‐dimer formation of oligothiophene radical cations took place more readily for the polymer films than for the monomers in solution. This new family of methacrylate polymers containing pendant oligothiophenes constitutes a new class of potential electrochromic materials, undergoing reversible, clear color changes on electrochemical oxidation and reduction.