Paper Number
SC28 

Session
Suspensions, Colloids, and Granular Materials

Title
Quantifying order in nonspherical colloidal systems with small-angle scattering

Presentation Date and Time
October 22, 2019 (Tuesday) 5:25

Track / Room
Track 2 / Room 304

Authors (Click on name to view author profile)

  1. Corona, Patrick T. (University of California, Santa Barbara, Chemical Engineering)
  2. Silmore, Kevin S. (MIT, Chemical Engineering)
  3. Lang, Christian (KU Leuven, Physics and Astronomy)
  4. Porcar, Lionel (Institut Laue-Langevin)
  5. Lettinga, M. Pavlik (KU Leuven, Physics and Astronomy)
  6. Swan, James (MIT, Chemical Engineering)
  7. Leal, L. Gary (University of California, Santa Barbara, Chemical Engineering)
  8. Helgeson, Matthew E. (University of California, Santa Barbara, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Patrick T. Corona1, Kevin S. Silmore2, Christian Lang3, Lionel Porcar4, M. Pavlik Lettinga3, James Swan2, L. Gary Leal1, and Matthew E. Helgeson1
1Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106; 2Chemical Engineering, MIT, Cambridge, MA 02139; 3Physics and Astronomy, KU Leuven, Leuven, Flanders, Belgium; 4Institut Laue-Langevin, Grenoble, France

Speaker / Presenter 
Corona, Patrick T.

Text of Abstract
The orientation of nonspherical particles in flow leads to a nonlinear rheological response that, in turn, affects the flows that develop. Measuring orientation of such systems can be challenging, especially when the particles are on nanometer length scales. Small-angle scattering (SAS) is a powerful technique that enables the measurement of fluid nanostructure on length scales from nanometers to microns and under rheometric flows. However, scattering measurements are made in ‘reciprocal-space’ with no means to simply relate scattering spectra to ‘real space’ structure. Therefore, structural models must be employed to extract information about the changes to fluid structure. As the first step toward understanding the relationship between measured scattering spectra and microstructural ordering; we examine the case of dilute, nonspherical, axisymmetric cylindrical particles in Stokes flow for which the orientation probability distribution functions (OPDFs) may be predicted. Analytical solutions for the scattering from oriented particles are derived and combined with numerical solutions for the OPDF to yield the scattering spectra in a variety of flows. We compare the predicted scattering spectra to rheo-SANS experiments on dilute fd-virus dispersions, where the model predictions with zero adjustable parameters show excellent agreement with experiments. Finally, we present a general method for fitting OPDFs using experimental SAS measurements and a model of the fluid microstructure without prescribing a form of the underlying OPDF. This method is demonstrated through the extraction of OPDFs from rheo-SANS experiments on semi-dilute fd-virus dispersions, where models for the full OPDF do not yet exist.