Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session F33: Morphology Characterization: Resonant X-ray ScatteringFocus
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Sponsoring Units: DPOLY Chair: Cheng Wang, Lawrence Berkeley National Laboratory Room: 505 |
Tuesday, March 3, 2020 8:00AM - 8:36AM |
F33.00001: BREAK
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Tuesday, March 3, 2020 8:36AM - 9:12AM |
F33.00002: Polymer Morphology Measurement by Polarized Resonant Soft X-ray Scattering Invited Speaker: Dean DeLongchamp In many polymers, the connection between morphology and performance is complex, and conventional materials structure measurements are not sufficient to provide a predictive structural model. Nanoscale variations in molecular orientation and composition, particularly in amorphous regions, are thought to be critical, but few techniques can probe them. I will describe our approach to polarized resonant soft X-ray scattering (P-RSoXS), which combines principles of soft X-ray spectroscopy, small-angle scattering, real-space imaging, and molecular simulation to produce a molecular scale structure measurement for soft materials and complex fluids. I will provide a complete description of our newly-constructed P-RSoXS measurement station at NIST beamlines of the National Synchrotron Light Source II. Results from model systems including commodity plastics, block copolymers, and semiconducting polymers will be discussed. An emphasis will be placed on connections between P-RSoXS and small angle neutron scattering (SANS), especially similarities in contrast variation approaches. I will conclude with our progress toward a forward-simulation framework that describes scattering length density at the nanoscale as a three-dimensional tensor. Results from this approach provide previously inaccessible orientation measurements of nanoscale amorphous regions in polymers. |
Tuesday, March 3, 2020 9:12AM - 9:24AM |
F33.00003: 12-ID – Soft Matter Interfaces (SMI) – A new resonant tender x-rays scattering Beamline at NSLS II Guillaume Freychet X-ray scattering is a powerful tool to study the structure and dynamics of soft matter on length scales from nanometers to millimeters and time scales from picoseconds to seconds. In the presentation, I will give a brief overview of the scattering techniques and instruments available at the new, high-brightness, NSLS-II synchrotron to study soft and biomaterials and then present the detailed design, parameters and the status of the Soft Matter Interfaces (SMI) beamline. SMI beamline capabilities on the tender x-ray regime will be highlighted since it enables resonant x-ray scattering measurements at the K-edges of key elements to bring new perspectives to the soft matter community: such as the P, Cl for water membrane problematics: Sulfur edge for organo-electronic filed; as well as K, Ca and more edges. The second part of the presentation will focus on a broad overview of the first results obtained at the beamline on a wide range of material, from organo-photovoltaic polymer to liquid membranes. Finally, the development of new in-situ stages, such as heating, shearing opens a wide field of possibilities. |
Tuesday, March 3, 2020 9:24AM - 9:36AM |
F33.00004: Molecular orientation in polyamide reverse osmosis membranes revealed by polarized resonant soft x-ray scattering Peter Beaucage Despite their broad application for water desalination, little is known about the fundamental interplay of synthesis, structure, and water transport in polyamide thin film composite membranes. The active layers of these materials are produced by interfacial polymerization atop a porous support resulting in films of typical thickness 100 nm with > 50 nm RMS roughness, making characterization by conventional techniques extremely challenging. Using polarized resonant soft x-ray scattering, a uniquely sensitive probe of molecular orientation and structure, we observe a striking degree of polarization-induced anisotropy in both commercial and model polyamide films. This anisotropy is likely due to local molecular orientation of C=C and C=O pi* electron systems. We compare orientation distributions and optical constants from P-RSoXS with those obtained by angle-dependent NEXAFS and demonstrate a new strategy for signal enhancement of interfacially oriented scattering. This previously-unreported molecular orientation may play a key role in connecting the processing and structure in polyamide thin film composite membranes to their water transport mechanisms, enabling enhanced performance in these important devices. |
Tuesday, March 3, 2020 9:36AM - 9:48AM |
F33.00005: Label-free characterization of aqueous molecular micelle nanostructure and dynamics via in-situ RSoXS Terry McAfee, Brian Akira Collins, Isvar Cordova, Cheng Wang, Thomas Ferron, Phillip Pickett Micelles are key to applications from drug delivery to commercial paints. Their nanostructure and dynamics are of critical importance to their macroscopic properties and functions, but are difficult to measure. Here we demonstrate a novel technique capable of such measurements based on Resonant Soft X-ray Scattering (RSoXS), which is uniquely capable of probing organic materials using their intrinsic chemical bonds rather than laborious and potentially disruptive labeling. Our customized nanofluidic cell enables RSoXS to be performed in liquid environments, allowing structure and dynamics to be measured in-situ for the intended application. We first apply the technique to a model system, Pluronic F127 micelles. Resonant energy contrast tuning allows the internal structure and composition to be measured quantitatively. We further investigate a novel amphiphilic statistical copolymer, “polysoap”, designed for oil spill remediation. Dynamic dual flow reveals an unexpected concentration dependence of the corona, which was not observed with traditional visible light scattering. We further show that despite aggregation, the unimeric core structure is retained, crucial for its application. |
Tuesday, March 3, 2020 9:48AM - 10:00AM |
F33.00006: Probing Buried Chemical Profiles in Novel EUV Resists with Energy-Tunable X-Rays Isvar Cordova, Luke Long, Guillaume Freychet, Cheng Wang, Patrick Naulleau With the adoption of extreme ultraviolet (EUV) lithography across the semiconductor industry, there comes a need to develop new resist materials that will become the mainstay enabling technology. This development places pressure on the metrology community to develop adequate non-destructive techniques capable of measuring the sub-10 nm patterns that such resists are meant to produce. Recent progress in grazing incidence and resonant x-ray scattering techniques have shown particular promise at being able to address part of these characterization challenges.1,2 |
Tuesday, March 3, 2020 10:00AM - 10:12AM |
F33.00007: Revealing Strain-Induced Conjugated Polymer Behaviors with Soft X-Ray Scattering and Spectroscopy Wenkai Zhong, Gregory Su, Qin Hu, Feng Liu, Wanli Yang, Thomas Russell, Cheng Wang Conjugated polymers have generated great interest due to their potential in the fabrication of deformable logic circuits that can be integrated into portable/wearable electronics. Here, we developed a beamline setup that can be capable of probing the bulk- and surface-sensitive data of polymer thin films during tensile test using soft x-ray. The combination of experimental and simulated x-ray spectroscopies assists to uncover the fingerprint of molecular behaviors under strain-stress measurement. Furthermore, to establish the relationship of the molecular evolution and device performances, the charge transport properties of the static strained thin film are also evaluated. We expect this work can contribute to understand the molecular origins of mechanical behaviors associated with the resulting device performances. |
Tuesday, March 3, 2020 10:12AM - 10:24AM |
F33.00008: Polarized resonant soft X-ray scattering reveals local chain orientation in polymer-grafted nanoparticles Subhrangsu Mukherjee, Jason Streit, Richard Arthur Vaia, Dean DeLongchamp Polymer-metal nanocomposites that are based on blends of metal NPs and matrix polymers face numerous design limitations and processing challenges. Polymer-grafted nanoparticles (PGNs) are of interest for applications ranging from structural to photonic and electrical. Many of the potential applications (coatings, adhesives, membrane separators, energy storage, etc.) necessitate co-optimization of functional performance with yield stress and toughness. An understanding of how the micro-architecture determines plasticity and failure modes in PGN assemblies is incomplete largely due to lack of tools to fully characterize the microstructure including local interfacial orientation. Here we show the measurement of local chain orientation in a PS-Au PGN system using polarized resonant soft X-ray scattering. The scattering anisotropy was observed at X-ray energies where the anisotropic contrast was affected by the Carbon K-edge 1s-π* resonance of the polystyrene phenyl group. Simple models of the particle geometry with forward simulation of the scattering pattern are consistent with phenyl ring orientation being ‘face on’ relative to the particle. |
Tuesday, March 3, 2020 10:24AM - 10:36AM |
F33.00009: Combining spectroscopy with DFT for optical models of polarized RSoXS to reveal molecular alignment in nanostructures Victor Murcia, Brian Akira Collins Polarized Resonant Soft X-ray Scattering (pRSoXS) is uniquely sensitive to local molecular orientation regardless of crystallinity, making it a powerful tool in characterizing various types of nanostructures. Unfortunately, it is difficult to interpret the scattering patterns due to a lack of appropriate optical models. Building block models (BBM), used to measure global orientation in X-ray absorption spectroscopy (XAS) won’t work for pRSoXS as it assesses differences in local ordering and means that XAS measurements alone will not provide enough information for an optical model. We have developed a model that combines angle-dependent XAS with density functional theory (DFT) to algorithmically create a biaxial optical tensor for molecules. We first show how the uniaxial approximation (UA) can be applied to the scattering anisotropy (SA) of Copper(II)Phthalocyanine (CuPc) films as measured by pRSoXS by expanding upon the BBM informed by DFT calculations. Then we show how the UA fails to describe the SA measured on poly-3-hexylthiophene (P3HT) films implying the need for a lower symmetry model. By combining DFT calculations with XAS, a model that enables extraction of additional details of local molecular orientation through pRSoXS can be developed. |
Tuesday, March 3, 2020 10:36AM - 10:48AM |
F33.00010: Control of solvent aggregation to impact active layer morphology and enhance performance in non-fullerene organic solar cells Guoyan Zhang, Sintu Rongpipi, Brooke Kuei, Enrique D Gomez The use of solvent additives in the active layer casting solution has proved to be an effective strategy to enhance the performance of solar cells. Solvent additives often have high boiling points, can enhance or reduce solubility, and thereby promote polymer aggregation in solution prior to spin-coating. As a consequence, the use of solvent additives can facilitate the crystallization process. The resulting ordered structure can remarkably increase charge photogeneration, carrier lifetime, and carrier mobility. |
Tuesday, March 3, 2020 10:48AM - 11:00AM |
F33.00011: Controlling Ionomer Phase Separation Through Side-Chain Engineering Gregory Su, Isvar Cordova, William White, Matthew Lindell, Michael Yandrasits, Lawrence Renna, Jun Feng, Shane Ardo, Cheng Wang, Ahmet Kusoglu Phase separation in perfluorinated ion-conducting polymer, or ionomer, membranes defines pathways for ion transport and controls overall conductivity. However, this phase-separated morphology is difficult to characterize and challenging to control based on molecular-level insights. Herein, we show two strategies to control phase-separation and domain spacing in perfluorinated ionomers, and resonant X-ray scattering is used to provide enhanced contrast and chemical sensitivity to decipher nanoscale morphology. Perfluoro ionene chain extended ionomers containing two or three ionic groups per side-chain exhibit tunable domain spacing based on side-chain length. Furthermore, the chain extended ionomers have greater long-range order and higher proton conductivity and water uptake compared to conventional perfluorinated sulfonic acid ionomers. Perfluorinated sulfonic acid iononers with photoacid dyes covalently bound to side-chain ends, which are promising for light-driven ion conduction, reveal a phase-separation length scale that increases with increasing dye content. Overall, these studies provide insights into detailed connections between polymer chemistry and phase-separated morphology to inform molecular-level design of next-generation membranes. |
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