Optical bandgaps and fluorescence resonance energy transfer studies of a series of poly(phenyleneethynylene) derivatives

In this paper, research work focuses on the synthesis of a series of PPE-based polymers with commonly used conjugated units, including thiophene, benzo[c][1,2,5]thiadiazole (BT), benzo[c][1,2,5]selenadiazole (BSe), etc. The optical bandgaps of these polymers were tuned in the range of 2.10-2.76 eV. The order of bandgap-lowering ability of these units in PPE-derivatives is: M-3 > M-6 > M-5 > M-4 > M-9 ≥ M-7, M-8 > M-2. Their FRET applications in polymer solar cell and TNT detection were studied respectively, and the results indicated that all these PPE-derivatives were good candidate materials for polymer solar cells or detecting TNT in solution. Furthermore, if electron-acceptor units had structures similar to the diphenylquinoxaline in the PPE-derivatives chain, the polymers would give a better fluorescence quenching in response to TNT compound. Polymers PPE-7 and PPE-8 were chosen as representative samples to investigate their photo-oxidative stability compared with that of PPVs or PTs. The results demonstrated that both polymers PPE-7 and PPE-8 were more photo-oxidatively stable than MEH-PPV or P3HT.