Abstract
It has long been established that the coherent scattering intensity of neutrons by isotropic mixtures of hydrogenous and deuterated polymers of matching molecular weights is, to the first approximation, proportional to the single-chain structure factor of the polymer chain. The validity of this fundamental relation for equilibrium, undeformed polymer melts is well supported by the extensive experimental and theoretical investigations over the past several decades. The generalization of this relation to the case of nonequilibrium, deformed polymer melts, however, is not a trivial one. Despite its widespread usage in small-angle neutron scattering (SANS) studies of deformed polymer melts, the assumed proportionality between coherent scattering intensity and single-chain structure factor has received very little experimental scrutiny. This work quantitatively examines this issue through spherical harmonic expansion analysis of the anisotropic SANS spectra of deformed polystyrene melts of different levels of deuterium labeling. It is shown that the classical assumption works extremely well over a wide range of scattering wavevectors, where the isotropic component of the SANS spectrum and the leading term of structural anisotropy vary by more than two orders of magnitude.
| Original language | English |
|---|---|
| Article number | 122698 |
| Journal | Polymer |
| Volume | 204 |
| DOIs | |
| State | Published - Sep 9 2020 |
Funding
This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). The research (Y.W.) is 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 synthesis, characterization, and small-angle neutron scattering experiments of the polystyrene samples were performed at Oak Ridge National Laboratory's Center for Nanophase Materials Sciences and Spallation Neutron Source, which are DOE Office of Science User Facilities. The research (Y.W.) is 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 synthesis, characterization, and small-angle neutron scattering experiments of the polystyrene samples were performed at Oak Ridge National Laboratory's Center for Nanophase Materials Sciences and Spallation Neutron Source, which are DOE Office of Science User Facilities.
Keywords
- Polymer melts
- Rheology
- Small-angle neutron scattering