@article{aba4530713fe4d11bc1dd078c9c70174,
title = "Understanding Solution State Conformation and Aggregate Structure of Conjugated Polymers via Small Angle X-ray Scattering",
abstract = "Donor-acceptor (D-A) conjugated polymers are high-performance organic electronic materials that exhibit complex aggregation behavior. Understanding the solution state conformation and aggregation of conjugated polymers is crucial for controlling morphology during thin-film deposition and the subsequent electronic performance. However, a precise multiscale structure of solution state aggregates is lacking. Here, we present an in-depth small-angle X-ray scattering (SAXS) analysis of the solution state structure of an isoindigo-bithiophene-based D-A polymer (PII-2T) in chlorobenzene and decane as our primary system. Modeling the system as a combination of hierarchical fibrillar aggregates mixed with dispersed polymers, we extract information about conformation and multiscale aggregation and also clarify the physical origin of features often observed but unaddressed or misinterpreted in small-angle scattering patterns of conjugated polymers. The persistence length of the D-A polymer extracted from SAXS agrees well with a theoretical model based on the dihedral potentials. Additionally, we show that the broad high q structure factor peak seen in scattering profiles can be attributed to lamellar stacking occurring within the fibril aggregates and that the low q aggregate scattering is strongly influenced by the polymer molecular weight. Overall, the SAXS profiles of D-A polymers in general exhibit a sensitive dependence on the co-existence of fibrillar aggregate and dispersed polymer chain populations. We corroborate our findings from SAXS with electron microscopy of freeze-dried samples for direct imaging of fibrillar aggregates. Finally, we demonstrate the generality of our approach by fitting the scattering profiles of a variety of D-A polymers based on thieno-isoindigo (PTII-2T), diketopyrrolopyrrole (DPP2T-TT, DPP-BTZ, PDPP2FT-C16), naphthalenediimide (P(NDI2OD-T2)), and a conjugated block copolymer P3HT-b-DPPT-T. The results presented here establish a picture of the D-A polymer solution state structure and provide a general method of interpreting and analyzing their scattering profiles.",
author = "Kwok, {Justin J.} and Park, {Kyung Sun} and Patel, {Bijal B.} and Rishat Dilmurat and David Beljonne and Xiaobing Zuo and Byeongdu Lee and Ying Diao",
note = "Funding Information: J.J.K and Y.D. acknowledge support by the NSF CAREER award under grant #18-47828. J.J.K. also acknowledges support from the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DE-SC0014664. K.S.P. and Y.D. acknowledge ONR support under Grant No. N00014-19-1-2146 and Grant No. N00014-22-1-2202, and K.S.P. acknowledges partial support from the Shen Postdoctoral Fellowship. B.B.P. and Y.D. acknowledge NSF DMREF for funding, under Grant Number 17-27605. The work in Mons was supported by the European Union{\textquoteright}s Horizon 2020 research and innovation programme under Marie Sklodowska Curie Grant agreement No.722651 (SEPOMO project). Computational resources were provided by the Consortium des {\'E}quipements de Calcul Intensif (C{\'E}CI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fed{\'e}ration Wallonie-Bruxelles, infrastructure funded by the Walloon Region under Grant Agreement No. 1117545. D.B. is a FNRS Research Director. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Extraordinary facility operations were supported in part by the DOE Office of Science through the National Virtual Biotechnology Laboratory, a consortium of DOE national laboratories focused on the response to COVID-19, with funding provided by the Coronavirus CARES Act. Funding Information: J.J.K and Y.D. acknowledge support by the NSF CAREER award under grant #18-47828. J.J.K. also acknowledges support from the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DE-SC0014664. K.S.P. and Y.D. acknowledge ONR support under Grant No. N00014-19-1-2146 and Grant No. N00014-22-1-2202, and K.S.P. acknowledges partial support from the Shen Postdoctoral Fellowship. B.B.P. and Y.D. acknowledge NSF DMREF for funding, under Grant Number 17-27605. The work in Mons was supported by the European Union's Horizon 2020 research and innovation programme under Marie Sklodowska Curie Grant agreement No.722651 (SEPOMO project). Computational resources were provided by the Consortium des {\'E}quipements de Calcul Intensif (C{\'E}CI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fed{\'e}ration Wallonie-Bruxelles, infrastructure funded by the Walloon Region under Grant Agreement No. 1117545. D.B. is a FNRS Research Director. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Extraordinary facility operations were supported in part by the DOE Office of Science through the National Virtual Biotechnology Laboratory, a consortium of DOE national laboratories focused on the response to COVID-19, with funding provided by the Coronavirus CARES Act. Publisher Copyright: {\textcopyright} 2022 American Chemical Society.",
year = "2022",
month = jun,
day = "14",
doi = "10.1021/acs.macromol.1c02449",
language = "English (US)",
volume = "55",
pages = "4353--4366",
journal = "Macromolecules",
issn = "0024-9297",
publisher = "American Chemical Society",
number = "11",
}