Paper Number
ET11 

Session
Advanced Experimental Techniques/Methods in Rheology

Title
Probing nanostructure under controlled complex deformations with neutron scattering in a fluidic four-roll mill

Presentation Date and Time
October 15, 2018 (Monday) 4:10

Track / Room
Track 5 / San Felipe Room

Authors (Click on name to view author profile)

  1. Corona, Patrick T. (University of California, Santa Barbara)
  2. Ruocco, Nino (University of California, Santa Barbara)
  3. Weigandt, Katie M. (NIST, Center for Neutron Research)
  4. Leal, L. Gary (University of California, Santa Barbara)
  5. Helgeson, Matthew E. (University of California, Santa Barbara)

Author and Affiliation Lines (in printed abstract book)
Patrick T. Corona1, Nino Ruocco1, Katie M. Weigandt2, L. Gary Leal1, and Matthew E. Helgeson1
1University of California, Santa Barbara, Santa Barbara, CA 93106; 2Center for Neutron Research, NIST, Gaithersburg, MD 20899

Speaker / Presenter 
Corona, Patrick T.

Text of Abstract
Industrial processing of complex fluids involves a wide range of flow histories that change the material’s nanostructure and, therefore, the properties of the final product. Current means for measuring flow-induced nanostructure have focused primarily on measurements in purely shearing or extensional deformations, which fail to capture the highly nonlinear behavior of soft materials under more realistic flows. To overcome this limitation, we have developed a new fluidic four roll mill (FFoRM) device for measurements of flow-induced structural changes in variable, near-2D deformation fields. The device, based on a previously designed fluidic four-roll mill, has been modified to produce well-controlled, uniform flows for in situ small-angle neutron scattering (SANS) measurements on fluids with a range of rheological responses including shear thinning and thickening, as well as viscoelasticity and yield stresses. As a test of these capabilities, we apply SANS in the FFoRM to characterize the non-equilibrium microstructure of a dispersion of cellulose nanocrystals (CNC) in flows with a range of deformation types. Particle tracking velocimetry verifies the ability to produce flow fields of arbitrary deformation type in these dispersions. Subsequent FFoRM-SANS measurements are combined with scattering models for oriented particles to determine the orientation distribution of the dispersion over a wide range of deformation types and rates. The results are consistent with a rheological model for semi-dilute colloidal rod dispersions, verifying the ability of FFoRM-SANS to characterize the flow-induced microstructure of complex fluids in response to a range of programmable deformations.