SYNTHESIS AND ELECTROLUMINESCENT PROPERTIES OF A POLYFLUORENE GRAFTED OLIGO(PHENYLENEVINYLENE DERIVATIVE WITH TWO TRIPHENYLAMINE SIDE GROUP)

Abstract

A polyfluorene derivative containing a monomer with bis-aldehyde functional group was synthesized according to Suzuki coupling reaction. Then,a small amount of oligo ( phenylenevinylene with two triphenylamine side group) ( MOPV) with bis-phosphonate functional groups was grafted to the polyfluorene derivative with bis-aldehyde functional groups by using Wittig-Horner method. The structures,thermal,optical and electrochemical properties of MOPV,pre-grafted polymer P1 and the grafted polymer PF-g-MOPV were characterized by 1H-NMR,GPC,DSC,TGA,UV-Vis,photoluminescence ( PL ) spectroscopy and cyclic voltammetry (CV),respectively. The grafted polymer exhibited better thermal properties than the pre-grafted polymer P1. The grafted polymer exihibited two PL emission bands ascribed to polyfluorene and MOPV segments,which indicated that Frster energy transfer from polyfluorene host to MOPV guest was efficient. This is the main mechanism in the PL process. To investigate the electroluminescent ( EL) characteristics of the grafted polymer,a single-layer PLEDs device with a configuration of indium tin oxide ( ITO ) /poly-(ethylenedioxythiophene):poly(styrenesulfonic acid) ( PEDOT∶ PSS) /polymer/Ca/Al was fabricated. The grafted polymer emitted yellowish-green light with the international commission on illumination ( CIE ) coordinates of (0. 30,0. 57 ) and the maximum brightness of 1550 cd /m2. The MOPV segments serve as effective sites for charge trapping,which can trap both electron and hole from the polyfluorene backbone. Charge trapping rather than Frster energy transfer is the main mechanism in the EL process.