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MA02.04.02 : Solvent-Vapor Annealing of Single Conjugated-Polymer Nanoparticles

2:00 PM–2:15 PM Apr 4, 2018

PCC West, 100 Level, Room 102 BC

Description
John Lupton1

1, University of Regensburg, Regensburg, , Germany

Single-molecule spectroscopy has provided unprecedented access to underlying structure-function relations of highly disordered conjugated polymers such as P3HT [1], but is often considered of only limited utility in illuminating molecular characteristics in the solid state. This perception has changed with the introduction of single-molecule solvent-vapor annealing techniques, which allow the deterministic growth of multichain aggregates – mesoscopic nanoparticles – to mimic bulk material characteristics while retaining the low degree of heterogeneity characteristic of a sub-ensemble experiment. Such single aggregates reveal that exciton generation in bulk films is an inherently intermolecular process, involving scores of polymer chains because of the prevalent process of singlet-singlet annihilation. As a consequence, even large aggregates containing many polymer chains exhibit deterministic single-photon emission in the form of photon antibunching [2]. A corollary of this effect is strong triplet-polaron quenching in large multichain aggregates, which leads to the disappearance of triplet-exciton photon correlation signatures in particles grown by controlled solvent-vapor annealing [3].

Most recently, it has become possible to directly image the growth and arrangement of multichain aggregates during annealing. Annealing promotes chain ordering, which strengthens the intrinsic J-aggregate character of polymer chains. Once the solvent molecules are removed by drying, cofacial stacking of these carefully ordered chains is encouraged, which gives rise to pronounced H-aggregate spectral characteristics. This drying process, on the level of single nanoparticles, is highly reversible and can be repeated many times to show a controlled switching between J- and H-type characteristics. Single-particle annealing therefore offers a unique window to monitoring the dynamics of solvent removal from polymer films, in real time, during processing [4].

[1] Thiessen, Vogelsang, Lupton et al., PNAS 110, 3550 (2013)
[2] Stangl, Vogelsang, Lupton et al., PNAS 112, 5560 (2015)
[3] Steiner, Lupton, Vogelsang, JACS 139, 9787 (2017)
[4] Eder, Vogelsang, Lupton et al., Nature Comm. 10.1038/s41467-017-01773-0 (2017)

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