The photo-optical and electrochemical activity promoted by trifluoromethyl-substituted and ortho-catenated triphenylamine core in poly(ether-imide)s

Abstract

A new series of five thermally and dimensionally stable aromatic poly(ether-imide)s consisting of an electron donating ortho-catenated triphenylamine (TPA) derivative bearing two trifluoromethyl groups and various electron-accepting phthalimide moieties were synthesized and thoroughly investigated. These polyimides display excellent organosolubility, unexpectedly even in ethanol, which allows their processing in environmentally friendly conditions. The twisting of the backbone structure induced by the ortho-catenated TPA core significantly affects their electronic properties. It was found that the CF3-substituted TPA moiety may facilitate dual intramolecular charge transfer (ICT) transitions, an aspect not highlighted yet for this class of polymers. In addition, we brought evidence for the occurrence of Förster excitation energy transfer (FRET) between the two ICT excited states that modulates the light emission toward the green-yellow spectral range, another novelty encountered at these polymers. The electron-withdrawing CF3 units directly graphthed on the triphenylamine core induced a fine-tuning of HOMO-LUMO energy levels, leading to low LUMO levels and energy band gaps. The novel characteristics endow the developed polymers with a wide application prospect, especially in the field of biology and opto-electronics.