Novel poly(phenylene ethynylene)-type conjugated polymers containing diketopyrrolopyrrole or triphenylpyrazoline units in the main chain: synthesis, characterization and photophysical properties

BACKGROUND: Polymer-based light emitting diodes (PLEDs) have received considerable attention as they combine the good mechanical and processing properties of polymers with semiconducting behavior, and can be easily fabricated as flexible devices. To obtain high-performance PLED materials by balancing the carrier injection of poly(phenylene ethynylene)s (PPEs), polymers containing two aryl-heterocyclic rings, namely diketopyrrolopyrrole (DPP) or triphenylpyrazoline (TPP), have been synthesized and investigated. RESULTS: PPE-type polymers containing DPP or TPP units were synthesized using Heck-Sonogashira coupling methodology and characterized by H-1 NMR, Fourier transform infrared and UV-visible spectroscopies, elemental analysis, gel permeation chromatography, photoluminescence (PL), X-ray diffraction, thermogravimetic analysis and cyclic voltammetry. The polymers obtained are easily soluble in common solvents and form smooth and uniform films. They are yellow or red emitters as revealed by PL. In addition, they show large Stokes shifts, which is in agreement with their twisted molecular structures determined via quantum chemical calculations. CONCLUSION: PPE-type polymers containing DPP or TPP units were successfully synthesized by coupling polymerization. They exhibit band gaps of 1.73 and 2.37 eV, respectively, and show potential as PLED materials. In addition, DPP-containing polymers with a very low band gap could be applied as potential photovoltaic materials. (c) 2009 Society of Chemical Industry