Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C03: Morphology Characterization: Frontier of Scattering and MicroscopyFocus Live
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Sponsoring Units: DPOLY GSNP DBIO Chair: Xiaodan Gu, University of Southern Mississippi; Cheng Wang, Lawrence Berkeley National Lab |
Monday, March 15, 2021 3:00PM - 3:12PM Live |
C03.00001: Mesoatomic distortions and subdomain morphology in DG and DD networks Edwin Thomas, Xueyan Feng, Christopher Burke, Abhiram Reddy, Gregory M Grason Slice-and-view scanning electron microscopy tomography was used to assess the 3D structural features of double gyroid (DG) and double diamond (DD) networks formed with two strongly segregated polystyrene-b-polydimethylsiloxane samples (χN~180). Due to shrinkage forces from solvent evaporation, both nominally cubic structures showed variable-triclinic unit cells by X-ray scattering and 3D reconstruction. The deformation is accommodated by non-affine modes of sub-unit cell symmetry breaking whereby the relatively soft strut lengths and diameters deform while the angular geometry between adjacent struts is stiff. Measurements included unit cell parameters, angular geometry of the minority network skeleton, the curvatures of the Intermaterial Dividing Surface (IMDS) and the subdomain thicknesses as measured from the IMDS to the skeletal graph or to the medial surfaces for both tubular (minority) and matrix (majority) phases. The distributions of medial thickness for the minority component are much shorter and more narrowly distributed than for the corresponding skeletal metrics. These subdomains morphology metrics are compared to self-consistent field predictions, suggesting |
Monday, March 15, 2021 3:12PM - 3:24PM Live |
C03.00002: Atomic-scale imaging of the effect of side-chain chemistry on the crystal motifs in polypeptoid nanosheets Morgan Seidler, Nan Li, Sunting Xuan, Ronald Zuckermann, David Prendergast, Xi Jiang, Nitash Balsara Polypeptoids are sequence-defined polymers that have received considerable attention as a platform to create biomimetic nanomaterials. When varying the side chain chemistry of an amphiphilic peptoid between hydrogen, fluorine, chlorine, bromine, and iodine, the arrangement of the polypeptoid molecules in a self-assembled crystalline nanosheet changes; this change cannot be revealed by conventional X-ray scattering or diffraction techniques due to the lack of phase information in position space. However, by combining low-dose cryo-TEM with crystallographic and single-particle image analysis techniques, we are able to reconstruct atomic-scale images of the crystal motifs of polypeptoid nanosheets. The different crystal motifs are interpreted in light of electronegativity, steric hindrance, and non-bonded internal energy obtained by molecular dynamic simulations. Precise engineering of polymer nanomaterials is enabled with this understanding of the competing factors that determine the polypeptoid crystal motifs at the atomic level. |
Monday, March 15, 2021 3:24PM - 3:36PM Live |
C03.00003: Three-dimensional Cryogenic Electron Microscopy Imaging of Two-dimensional Polymer Crystals Xi Jiang, Sunting Xuan, Nan Li, David Prendergast, Ronald Zuckermann, Nitash Balsara, Kenneth Downing We introduce a novel composite holey gold support that prevents cryo-crinkling and reduces beam-induced motion of two-dimensional specimens. The experiments are conducted on self-assembled crystalline polypeptoid nanosheets. Low-dose cryogenic electron microscopy micrographs are obtained from frozen hydrated crystalline nanosheets on the novel ultra-flat support at different tilting angles. A hybrid processing of crystallographic, tomography and single particle methods, developed for cryo-electron microscopy of biological macromolecules, is used to resolve the structure of crystals at atomic level. Our approach is robust and enable direct visualization of the spatial arrangement of atoms in backbones and side chains in the three-dimensional reconstructed crystalline polypeptoid nanosheet. |
Monday, March 15, 2021 3:36PM - 4:12PM Live |
C03.00004: Combining Advanced Experimental Methods to Characterization of Polymer Nanocomposites Invited Speaker: Karen Winey Each characterization method provides specific information about a polymer sample over a limited range of length and time scales. A comprehensive understanding of polymer morphology and dynamics is best developed by combining a set of characterization methods to capture a broader range of lengths and times. This talk will highlight examples from our studies of polymer nanocomposites that have combined methods to develop detailed and quantitative descriptions of these complex polymer systems. Specifically, the dynamics in polymer nanocomposites include segmental and chain-scale motion of the polymer, as well as diffusion of the nanoparticles. We apply ion beam methods (elastic recoil detection and Rutherford backscattering) and single particle tracking methods, as well as more accessible methods such as temperature-modulated DSC and broadband dielectric spectroscopy methods, to probe the molecular weight dependence of the polymer and nanoparticles are revealed for nanoparticles of various sizes and nanoparticle-polymer interactions. These vignettes will also serve to illustrate the capabilities of the individual methods and demonstrate the exceptional value of combining these advanced experimental methods. |
Monday, March 15, 2021 4:12PM - 4:24PM Live |
C03.00005: 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. |
Monday, March 15, 2021 4:24PM - 4:36PM Live |
C03.00006: Update on resonant tender x-rays scattering user programm at the Soft Matter Interfaces beamline at NSLS II Guillaume Freychet, Mikhail Zhernenkov 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 [1], a long energy range canted in-vacuum undulator (IVU) beamline at NSLS-II. 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. |
Monday, March 15, 2021 4:36PM - 4:48PM Live |
C03.00007: Quantification of flow-induced phase separation in polymer blends by small-angle neutron scattering Yangyang Wang, Weiyu Wang, Kunlun Hong, Yun Liu Flow-induced mixing, demixing, and phase transition phenomena in polymeric liquids are ubiquitous and practically important. This study demonstrates how the flow-induced phase separation can be quantitatively studied by applying the spherical harmonic expansion technique to small-angle neutron scattering. Using 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 viscoelastic phase separation. The increasing spatial fluctuation of concentration is 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 towards low wavenumbers. Additionally, the spherical harmonic expansion framework permits real-space analysis in a convenient form. The methodology described in this work provides a concrete venue for quantitative studies of phase transitions of polymeric fluids under deformation and flow via small-angle scattering techniques. |
Monday, March 15, 2021 4:48PM - 5:00PM Live |
C03.00008: Computational Reverse Engineering Analysis of Scattering Experiments (CREASE) on Amphiphilic Block Polymer Solutions Michiel Wessels, Arthi Jayaraman In this talk we will present the extension of a recently developed Computational Reverse-Engineering Analysis for Scattering Experiments (CREASE) approach to analyze spherical, cylindrical, fibrillar, and elliptical cylinder assembled structures in amphiphilic block copolymer solutions. Using CREASE one can analyze scattering profiles when existing analytical models are insufficient to correctly interpret the shape and dimensions of the assembled solution structure and the chain conformations and packing within the assembled domains. CREASE is comprised of two steps: the first step involves a genetic algorithm (GA) to determine the shape and dimensions of the domains in assembled structure and the second step uses molecular simulations to reconstruct chain conformations and monomer level arrangements within the assembled structure. We will also demonstrate the integration of machine learning enhanced genetic algorithm step in the CREASE framework to speed up the CREASE calculation as well improve accuracy of the CREASE predictions. |
Monday, March 15, 2021 5:00PM - 5:36PM Live |
C03.00009: 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 3D tensor. Results from this approach provide previously inaccessible orientation information that impacts properties across a range of important material functions. |
Monday, March 15, 2021 5:36PM - 5:48PM Live |
C03.00010: Label-free characterization of aqueous micelle nanostructure, chemistry, and dynamics via in-situ RSoXS Brian Collins, Terry McAfee, Thomas Ferron, Isvar A Cordova, Phillip Pickett, Charles McCormick, Cheng Wang Micelles are key to nanocarrier applications from drug delivery to environmental remediation. Their structure and dyanmics are of critical importance to their 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 uniquely probes organic materials using their intrinsic chemical bonds rather than laborious and disruptive labeling. Our customized microfluidic cell enables RSoXS to be performed in liquid environments, allowing structure and dynamics to be measured in-situ. We first apply the technique to a model smart medicine platform, Pluronic F127. Resonant contrast tuning allows the internal structure and chemical composition to be measured quantitatively without labeling. We further investigate a novel amphiphilic statistical copolymer designed for oil spill remediation. Dynamic dual flow reveals an unexpected concentration dependence of the corona, which was not resolved with traditional visible light scattering. We further show that despite aggregation, the unimeric bridged-core structure is retained at all concentrations, crucial for its application. |
Monday, March 15, 2021 5:48PM - 6:00PM On Demand |
C03.00011: Self-assembly of Frank-Kasper Phases in Conformationally Asymmetric Fluorinated Block Copolymers Seungbae Jeon, Taesuk Jun, Seongjun Jo, Hyungju ahn, Byeongdu Lee, Du Yeol Ryu In recent years, various of Frank-Kasper (FK) phases which were originally observed in metal alloys have been discovered in many soft materials. Theoretical and experimental studies have revealed that conformational asymmetry (ε) of the different blocks provides a key mechanism to stabilize the FK σ and A15 phases between hexagonally packed cylinder (HEX) and body centered cubic (BCC) phases in block copolymers (BCPs) self-assembly. Herein, polydimethylsiloxane-b-poly(2,2,2-triflouroethyl acrylate)s (PDMS-b-PTFEAs) were designed using flexible silicon-containing blocks and rigid fluorine-containing blocks to produce high conformationally asymmetric BCPs. Evaluated value of ε was 2.20 which is relatively higher than other previously published BCPs. A series of PDMS-b-PTFEAs were synthesized to produce compositionally asymmetric core PTFEA and the corona PDMS blocks. Using small-angle X-ray scattering, the FK σ and C14 phases were observed between HEX and BCC phases. Since the stability of σ phase increases by the value of ε, we speculate that the stability level of the C14 phase as well as σ phase is due to the relatively high ε of PDMS-b-PTFEAs. |
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