Heterogeneous dynamics in a polymer solution revealed through measurement of ultraslow convection

Newton, vol. 2, pp. 100464

Abstract

Understanding solution-phase aggregation and dynamics in complex fluids is critical for material processing, yet widely used dynamic light scattering (DLS) is unsuitable for strongly attenuating systems such as conjugated polymers. We use X-ray photon correlation spectroscopy (XPCS) to probe the dynamics of a polymer, PM7, in toluene, revealing unexpected oscillations in the autocorrelation function that show vertical flow during measurement. Despite the relatively low X-ray absorption, measured flow velocities scale with X-ray power and suggest convective transport. Our analyses reveal mobile and static scatterers that together produce oscillatory, heterodyne features in the correlation functions. Finite element simulations predict flow velocities much larger than observed, suggesting that entanglements of the aggregates slow their motion. These results provide a direct measurement of ultraslow convection and highlight the need to account for even modest beam heating in XPCS analysis. Moreover, the observation of distinct scatterer populations underscores the structural complexity of conjugated polymer solutions.

Authors 12

1. Thomas P. Chaney

   University of Colorado Boulder

   Affiliation as printed

   Materials Science and Engineering, University of Colorado, Boulder, CO 80309, USA

2. Samuel D. Marks

   University of Colorado Boulder

   Affiliation as printed

   Materials Science and Engineering, University of Colorado, Boulder, CO 80309, USA

3. Dylan M. Ladd

   University of Colorado Boulder

   Affiliation as printed

   Materials Science and Engineering, University of Colorado, Boulder, CO 80309, USA

4. Andrei Fluerasu

   Brookhaven National Laboratory · National Synchrotron Light Source II

   Affiliation as printed

   National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY 11973-5000, USA

5. Federico Zontone

   European Synchrotron Radiation Facility

   Affiliation as printed

   ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex, France

6. Yuriy Chushkin

   European Synchrotron Radiation Facility

   Affiliation as printed

   ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex, France

7. Sebastian Frücht Aachen Institute of Physical Chemistry

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Institute for a sustainable Hydrogen Economy (IHE-1), Forschungszentrum Jülich, An der Deutschen Welle 7a, 52428 Jülich, Germany

   Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany

8. Dina Sheyfer

   Argonne National Laboratory

   Affiliation as printed

   X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA

9. Kelsey Levine

   University of Colorado Boulder

   Affiliation as printed

   Materials Science and Engineering, University of Colorado, Boulder, CO 80309, USA

10. Amnahir E. Peña-Alcántara

    Stanford University

    Affiliation as printed

    Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA

11. Hans‐Georg Steinrück corresponding Aachen Institute of Physical Chemistry

    Forschungszentrum Jülich · Paderborn University · RWTH Aachen University

    Affiliation as printed

    Department of Chemistry, Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany

    Institute for a sustainable Hydrogen Economy (IHE-1), Forschungszentrum Jülich, An der Deutschen Welle 7a, 52428 Jülich, Germany

    Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany

12. Michael F. Toney corresponding

    University of Colorado Boulder

    Affiliation as printed

    Department of Chemical and Biological Engineering and Renewable and Sustainable Energy Institute (RASEI), University of Colorado, Boulder, CO 80309, USA

    Materials Science and Engineering, University of Colorado, Boulder, CO 80309, USA