| Autor: |
Candeias, L. P., Wildeman, J., Hadziioannou, G., Warman, J. M. |
| Zdroj: |
The Journal of Physical Chemistry - Part B; September 2000, Vol. 104 Issue: 35 p8366-8371, 6p |
| Abstrakt: |
The triplet excited states (3Bu) of phenyl-capped, n-octyloxy substituted p-phenylenevinylene oligomers have been generated by pulse radiolysis in benzene at room temperature. They were characterized by their UV/vis absorption spectra, kinetics of formation and decay, and quenching by oxygen. The triplet states were formed either by energy transfer from the solvent excited singlet followed by inter-system crossing (φISC ≈ 0.06) or by energy transfer from the naphthalene triplet. They exhibited a strong absorption (ε ≈ 105 M-1 cm-1) at photon energies that depended strongly on the chain length. Comparison with poly(2-methoxy-5-(2-ethylhexoxy)-p-phenylenevinylene) (MEH−PPV) suggests that the conjugation in the polymer extends over approximately 15 monomer units, i.e., similar to the conjugation length in the solid state at low temperature. In oxygen-free solution, the triplets had lifetimes of the order of tens of microseconds. They were quenched by oxygen with bimolecular rate constants of ca. 109 M-1 s-1. Radical-anions and radical-cations of the shorter oligomers could also be observed. The radical-anions were efficiently quenched by oxygen (k ≈ 1010 M-1 s-1), while the radical-cations were unaffected by O2. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
|
