Abstract
This study demonstrates how the large concentration fluctuations of polymeric liquids under deformation and flow can be quantitatively studied by applying the spherical harmonic expansion technique to small-angle neutron scattering. Using a series of binary polymer blends, it is shown that the emergence of the so-called butterfly patterns is caused by the change of sign in the leading anisotropic component of the small-angle spectrum, when the scattering is dominated by intermolecular correlation associated with flow-induced demixing. The increasing spatial fluctuations of concentration are evidenced by the enhancement of the isotropic component of the scattering spectrum in the zero-angle limit and peak shift of the leading anisotropic coefficients toward low Q. Additionally, the spherical harmonic expansion framework permits real-space analysis of anisotropic scattering length density correlation in a convenient form. The methodology described in this work provides a concrete venue for quantitative studies of phase behavior of fluids under deformation and flow via small-angle scattering techniques, where mainly qualitative approaches were previously employed.
| Original language | English |
|---|---|
| Pages (from-to) | 3531-3542 |
| Number of pages | 12 |
| Journal | Macromolecules |
| Volume | 54 |
| Issue number | 7 |
| DOIs | |
| State | Published - Apr 13 2021 |
Bibliographical note
Publisher Copyright:© 2021 American Chemical Society.
Funding
The research was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Early Career Research Program Award KC0402010, under Contract DE-AC05-00OR22725. The polymer synthesis and rheological characterization were performed at Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. SANS measurement of the isotropic PS30K sample used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Access to NGB 30m SANS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement no. DMR-1508249. Certain commercial equipment, instruments, or materials are identified in this document. Such an identification does not imply recommendation or endorsement by the National Institute of Standards and Technology nor does it imply that the products identified are necessarily the best available for the purpose.
| Funders | Funder number |
|---|---|
| National Science Foundation | DMR-1508249 |
| U.S. Department of Energy | |
| National Institute of Standards and Technology | |
| Office of Science | |
| Basic Energy Sciences | DE-AC05-00OR22725, KC0402010 |