Synthesis and preliminary characterization of novel naphthalene bisimide based copolymers

Here we report the synthesis and preliminary characterization of three novel conjugated 2,6-(naphthalene-1,4,5,8-tetracarboxylic-N,N′-dialkyldiimide) based copolymers with π-conjugation throughout the main chain. Two (PNATF and PNTTOF) copolymers were polymerized through Suzuki type cross-coupling reactions, the other (PNATT3) via a Stille-type reaction. The modifications of the side chain on the naphthalene bisimide unit and the thiophene contents in the polymer backbone were investigated. The structures of these polymers were confirmed by NMR. PNATF and PNTTOF could be dissolved in common solvents such as toluene, CHCl3 and 1,2-dichlorobenzene. The optical spectra of the three copolymers revealed that they had two strong absorption bands at 386–394 and 600–670 nm. The photoluminescence spectra of PNATF and PNTTOF showed a weak red emission. The band gap values of the copolymer films determined from electrochemical and optical measurements were in good agreement, ranging between 1.58–1.88 and 1.53–1.69 eV, respectively. From these data we suggest these three copolymers are worthy of further investigation as potential candidates for applications in electronic devices.