A new low band gap dithienylene-fluorovinylene electrochromic polymer: an intriguing effect of silyl substitution on the polymerisation reaction

Trimethylsilyl substitution at the a position has been claimed to favour both the chemical and electrochemical polymerisation processes of polythiophenes. When comparing the electro-polymerisation of three related monomers we found that the above is not a general rule: the trimethylsilyl substitution does not always produce the expected results because electronic effects play an intriguing role in directing the reaction. One of the three monomers, 1,2-difluoro-1,2-bis(4-methoxy-2-thienyl)ethene, easily underwent electropolymerisation giving a new low band gap polymer with good electrochromic properties.