title: Exciton-Exciton Annihilation as a Probe of Interchain Interactions in PPV-Oligomer Aggregates.
abstract: One measure of exciton mobility in an aggregate is the efficiency of exciton-exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH-PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed from the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. The wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.
authors.affiliation: Department of Chemistry, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Linda A
authors.identifier: 0000-0003-0075-6521
authors.initials: LA
authors.lastname: Peteanu
authors.affiliation: Department of Chemistry, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Sanchari
authors.identifier: 0000-0002-9875-1026
authors.initials: S
authors.lastname: Chowdhury
authors.affiliation: Zernike Institute of Advanced Materials , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Jurjen
authors.initials: J
authors.lastname: Wildeman
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Matthew Y
authors.identifier: 0000-0001-5619-5722
authors.initials: MY
authors.lastname: Sfeir