Low band gap-conjugated polymer derivatives

Three new poly(4,4-dialkylcyclopentadithiophene (PDOCPT) derivatives, poly(4,4-dialkylcyclopentadithiophene-co-pyridine) (PDOCPTPy), poly(4,4-dialkylcyclopentadithiophene-co-phenanthroline) (PDOCPTPh), and poly(cyclopenta[2,1-b:3,4-b′]dithiophen-4-one) (PDOCPTCK) were prepared. They were synthesized form the Stille coupling of 2,7-bis-trimethyltin-4,4- dialkylcyclopentadithiophene with dibromopyridine and dibromophenanthroline, respectively. They are soluble in organic solvents, such as CHCl₃ and Toluene. The absorption thresholds of these two polymers are 500 and 650 nm for PDOCPTPy and PDOCPTPh, respectively. The electronic absorption data suggested that the band gap energy of copolymer will fall in-between the individual homopolymers. This may give a cue on how to prepare soluble conjugated polymers with desirable band gap energy.