An investigation into the role of polarity of diamines in controlling the electron migration mechanism of photoluminescent poly(amide–imide)s

Abstract

Several diamines with remarkable different polarities were used to produce photoactive poly(amide–imide)s (PAI)s in a quantitative yield. The absorption, fluorescence and photophysical properties of series of poly(amide–imide)s containing fused aromatic systems as energy donor and energy acceptor with different diamines cores are described. Poly(amide–imide)s exhibit broad fluorescent characteristic, and its fluorescent intensity is related to the intermolecular chain–chain or chain–solvent interaction. The fluorescence spectra confirmed an efficient singlet–singlet energy transfer between fused aromatic systems. The self-quenching mechanism was studied according to the specific behavior of these polymers in different solvents. The self-quenching rate constant for the association reaction in the excited state (Kq) could be measured from the Stern–Volmer equation. The kind of fused system and diamines show different electron migration mechanisms and photoluminescent properties in the singlet-excited states. By using the exothermic energy transfer as a function of diamine polarity, the electron transfer mechanism was evaluated for aromatic poly(amide–imide)s. In principle, the fluorescence energy is absorbed by different (PAI)s and raises the molecules to one of its excited states. Afterwards this excitation energy transfers through the different relaxation channels, i.e. columbic or exchange energy transfer.