Abstract
Chain exchange in amphiphilic block polymer micelles is measurable with time-resolved small-angle neutron scattering (TR-SANS) where contrast-matched conditions reveal chain mixing as reduced intensity. However, analyzing chain mixing on short time scales e.g. during micelle transformations remains challenging. SANS model fitting can quantify chain mixing during size and morphology changes, however short acquisition times lead to lower data statistics (higher error). Such data are unsuitable for form factor fitting, especially with polydisperse and/or multimodal scenarios. An integrated-reference approach, R(t), is compatible with such data by using fixed reference patterns for the unmixed and fully mixed states that are each integrated to improve data statistics (lower error). Although the R(t) approach is tolerant of low data statistics, it remains incompatible with size and morphology changes. A new shifting references relaxation approach, SRR(t), is proposed where reference patterns are acquired at each time point to enable mixed state calculations regardless of short acquisition times. The additional experimental measurements needed are described which provide these time-varying reference patterns. The use of reference patterns makes the SRR(t) approach size/morphology-agnostic, allowing for the extent of micelle mixing to be directly calculated without this knowledge. SRR(t) is thus compatible with arbitrary levels of complexity and can provide accurate assessment of the mixed state which could support future model analysis. Calculated scattering datasets were used to demonstrate the SRR(t) approach during multiple size, morphology, and solvent conditions (scenarios 1-3). The mixed state calculated from the SRR(t) approach is shown to be accurate for all three scenarios.
| Original language | English |
|---|---|
| Journal | Soft Matter |
| DOIs | |
| State | Accepted/In press - 2023 |
Funding
T. L. and M. S acknowledge support by a National Science Foundation under NSF Award #DMR-1752615. This work made use of resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory (IPTS-21752.1 and IPTS 25337.1). M. S. acknowledges support by the Hanse-Wissenschaftskolleg Institute for Advanced Study, Delmenhorst, Germany. Neutron scattering research conducted at the Bio-SANS instrument, a DOE Office of Science, Office of Biological and Environmental Research resource (FWP ERKP291), used resources at the High Flux Isotope Reactor, a DOE Office of Science, Scientific User Facility operated by the Oak Ridge National Laboratory. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract DE-AC05-00OR22725. This manuscript has been coauthored 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 nonexclusive, paid-up, irrevocable, worldwide 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 ).