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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2019 Virgili, Botta, Mróz, Parrenin, Brochon, Cloutet, Pavlopoulou, Hadziioannou and Geoghegan.The photophysics of water and propan-1-ol suspensions of poly [N-9"-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2',1',3'- benzothiadiazole)] (PCDTBT) nanoparticles and mesoparticles has been studied by ultrafast spectroscopy. High molar mass polymer (HMM > 20 kg/mol) forms nanoparticles with around 50 nm diameter via mini-emulsion post-polymerization, while low molar mass (LMM < 5 kg/mol) polymer prepared by dispersion polymerization results in particles with a diameter of almost one order of magnitude larger (450 ± 50 nm). In this study, the presence of excited-states and charge separated species was identified through UV pump and visible/near-infrared probe femtosecond transient absorption spectroscopy. A different behavior for the HMM nanoparticles has been identified compared to the LMM mesoparticles. The nanoparticles exhibit typical features of an energetically disordered conjugated polymer with a broad density of states, allowing for delayed spectral relaxation of excited states, while the mesoparticles show a J-aggregate-like behavior where interchain interactions are less efficient. Stimulated emission in the red-near infrared region has been found in the mesoparticles which indicates that they present a more energetically ordered system.
Author(s): Virgili T, Botta C, Mroz MM, Parrenin L, Brochon C, Cloutet E, Pavlopoulou E, Hadziioannou G, Geoghegan M
Publication type: Article
Publication status: Published
Journal: Frontiers in Chemistry
Year: 2019
Volume: 7
Online publication date: 11/06/2019
Acceptance date: 20/05/2019
Date deposited: 19/12/2019
ISSN (electronic): 2296-2646
Publisher: Frontiers Media S.A.
URL: https://doi.org/10.3389/fchem.2019.00409
DOI: 10.3389/fchem.2019.00409
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