This work was supported by the National Science Foundation (CHE0070122), the Robert A. Welch Foundation and the Center for Materials Chemistry of the University of Texas. We gratefully acknowledge Prof. S. E. Webber for allowing us to use SPEX Fluorolog-τ2 spectrofluorometer and GPC facilities in his laboratory. The FTIR data were gathered using the facilities of the Center of Nano- and Molecular (CNM) Science and Technology of the University of Texas. We grateful acknowledge useful discussions with Barry Young, VP and CFO of DisplaySearch Corp.
On the Origin of Green Emission in Polyfluorene Polymers: The Roles of Thermal Oxidation Degradation and Crosslinking†
Article first published online: 2 SEP 2004
Copyright © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Advanced Functional Materials
Volume 14, Issue 8, pages 783–790, August, 2004
How to Cite
Zhao, W., Cao, T. and White, J. M. (2004), On the Origin of Green Emission in Polyfluorene Polymers: The Roles of Thermal Oxidation Degradation and Crosslinking. Adv. Funct. Mater., 14: 783–790. doi: 10.1002/adfm.200305173
- Issue published online: 2 SEP 2004
- Article first published online: 2 SEP 2004
- Manuscript Accepted: 31 MAR 2004
- Manuscript Received: 12 DEC 2003
- Green-light emitters;
The green emission of poly(9,9′′-dioctylfluorenyl-2,7′′-diyl), end-capped by polyhedral oligomeric silsequioxanes, (PFO-POSS) has been investigated by photoluminescence (PL) and photoexcitation (PE), gel permeation chromatography (GPC), and transmission Fourier transform infrared (FTIR) spectroscopy. The green emission is closely correlated with thermal oxidation degradation and crosslinking of the polymer and is enhanced by annealing at elevated temperatures. The green-to-blue emission intensity ratio, used to assess the emission properties of thin (90 nm) films, was 3.70, 4.35, and 1.54 for an air-annealed film, its insoluble residue (crosslinked), and a film cast from its soluble portion, respectively. For thick (5–6 μm) film, the ratios are 13.33, 13.33, and 0.79, respectively. However, FTIR spectroscopy of thick films leads to the conclusion that the carbonyl-to-aromatic ring concentration ratio are 0.018, 0.015, and 0.032, respectively. Focusing on the recast films, the green emission is relatively low while the carbonyl concentration is relatively high. This suggests that the energy traps at crosslinked chains play an important role in green emission. It is likely that the crosslinking enhances the excitation energy migration and energy transfer to the defects by hindering chain segment twisting.