Synthesis and Properties of Polymers Containing Charge Transport Pendant Group

Abstract

Non-conjugated polymers containing charge transporting pendant groups were synthesized and characterized. Poly(N-(4-vinylphenyl)-carbazole) (PPCZ) with a hole transporting carbazole group and poly(2-methylphenyl-5-(4-vinylphenyl)-1,3,4-oxadiazole) (PPOXD) with an electron transporting 1,3,4-oxadiazole group were synthesized by free radical polymerization of corresponding monomers, respectively, N-(4-vinylphenyl)-carbazole (VPCZ) and 2-methylphenyl-5-(4-vinylphenyl)-1,3,4-oxadiazole (VPOXD). Poly(vinyl carbazole) (PVK), well-known hole transporting material, was also prepared for comparison. These polymers with moderate molecular weight and molecular weight distribution were found to be all solution-processable. Thermal, optical and electrochemical properties of these polymers were investigated for an attempt to apply for charge transporting layer and/or host matrix in emitting layer in OLEDs. It appeared that photophysical properties such as ionization potential and electron affinity were dependent on respective pendant groups in polymers. High band gap energy levels (3.19 eV ∼3.44 eV) could make polymers a promising candidate for host matrix in OLEDs.

Keywords:

• 1,3,4-oxadiazole
• carbazole
• charge transport
• non-conjugated polymer
• OLED
• PVK

Acknowledgments

This work was supported by Daegu University Research Grant 2009.

Notes

^a Measured by using GPC with polystyrene standard calibration.

^b Temperature at 5 wt% loss based on initial weight.

^c Quantum yield in THF.

^d Calculated from the crosspoint of UV-Vis and PL spectra.

^e Measured by a RIKEN Keiki AC-2.

^f Estimated from the HOMO and band gap.