Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session C49: Advanced Morphological Characterization of Polymer II: X-ray and Neutron ScatteringFocus
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Sponsoring Units: DPOLY Chair: Brian Collins, Washington State University Room: BCEC 252A |
Monday, March 4, 2019 2:30PM - 2:42PM |
C49.00001: Role of Chain Length in the Formation of Frank-Kasper Phases in Diblock Copolymers Frank Bates, Ronald Lewis III, Akash Arora, Haley Beech, Bongjoon Lee, Aaron Lindsay, Timothy Lodge, Kevin Dorfman Formation of the Frank-Kasper (FK) sigma phase in compositionally asymmetric A-B diblock copolymer melts has been shown using self-consistent mean-field theory (SCFT) to be associated with conformational asymmetry, bA/bB > 1, where b is the statistical segment length. Small-angle X-ray scattering and rheological measurements performed with narrow dispersity poly(styrene)-b-poly(butadiene) (PS-PB) diblocks show an absence of the FK sigma phase whereas poly(ethylethylene)-b-poly(lactide) (PEE-PLA) diblocks exhibit a wide composition window of this complex phase, where both systems have bA/bB = 1.3. This behavior is associated with block self-concentration expressed through the invariant degree of polymerization N(bar) = Nb6/v2 in which v is the statistical segment volume. A direct analogy will be drawn between the role of N(bar) in FK phase formation in diblocks and the value Ne(bar) that defines the universal crossover from Rouse to reptation dynamics in homopolymer melts, where the block values of N(bar) for PEE-PLA and PS-PB are less than and greater than Ne(bar), respectively. |
Monday, March 4, 2019 2:42PM - 2:54PM |
C49.00002: PRISM Theory as an Accessible Model for Neutron and X-ray Scattering Experiments of Liquid-Like Polymer Systems Tyler Martin, Ronald Jones Polymer Reference Interaction Site Model (PRISM) theory is able to predict the structure and thermodynamics of a wide range of liquid-like polymer systems including polymer melts, blends, solutions, polyelectrolytes, and nanocomposites. Using single-molecule, intra-molecular correlations as input, past studies have used PRISM to model the experimental scattering data of concentrated solutions and melts, including data from small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering experiments (WAXS). Despite its utility in these studies, PRISM theory has remained inaccessible to many scientists seeking to extract thermodynamic and structural information from their scattering data of liquid-like polymer systems. Recently, we have released a computational tool called pyPRISM which aims to reduce the barrier to accessing PRISM theory and allow users to calculate structure factors and total scattering intensities from single-molecule scattering functions. In this talk, we will discuss the features and limitations of using PRISM theory as a scattering model by highlighting our efforts in using pyPRISM to create new models for the scattering of several systems including worm-like micelles, monoclonal antibodies, and bottlebrush polymers. |
Monday, March 4, 2019 2:54PM - 3:06PM |
C49.00003: Phase Behavior of Hybrid Inorganic-Organic Diblock Copolymer Electrolytes Gurmukh Sethi, Irune Villaluenga, Nitash Balsara Solid polymer electrolytes are advantageous for applications in lithium batteries due to improved chemical stability compared to organic liquid electrolytes. Diblock copolymer electrolytes offer highly tunable nanostructures with both soft, ion-conducting domains and mechanically rigid non-conducting domains. The phase behavior of poly(ethylene oxide) -block-polyhedral oligomeric silsesquioxane acrylate (PEO-POSS) mixed with lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt is studied by varying the diblock composition and salt concentration. Using small angle X-ray scattering (SAXS), the morphology and Flory-Huggins interaction parameter is obtained to quantify the thermodynamic interactions. PEO-POSS without salt exhibits a classical order-to-disorder transition. Adding salt dramatically changes the phase behavior and a disorder-to-order transition is observed upon heating. Upon further salt addition, a transition from lamellae to coexisting lamellae and hexagonally packed cylinders is observed. Our results suggest that the addition of salt plays a more complicated role in this hybrid organic/inorganic electrolytes in comparison to traditional all organic diblock copolymer electrolytes. |
Monday, March 4, 2019 3:06PM - 3:18PM |
C49.00004: In Situ Study of ABC Triblock Terpolymer Self-Assembly under Solvent Vapor Annealing Sangho Lee, Li-Chen Cheng, Kevin G. Yager, Muhammad Mumtaz, Karim Aissou, Caroline Anne Ross The morphological transition of core-shell cylinder-forming triblock terpolymers during solvent vapor annealing is monitored in situ using grazing-incidence small-angle X-ray scattering. We investigate the self-assembly behavior of two linear ABC triblock terpolymers, poly(1,1-dimethyl silacyclobutane-block-styrene-block-methyl methacrylate) (PDMSB-b-PS-b-PMMA or DSM) and poly(1,1-dimethyl silacyclobutane-block-styrene-block-lactide) (PDMSB-b-PS-b-PLA or DSL). The morphology, orientation, and period of the microdomains are characterized under a continuous vapor flow of CHCl3 as a function of deswelling rate and swelling ratio. Films of DSM form in-plane core-shell cylinders, while DSL films predominantly form vertically oriented core-shell cylinders. A reversible order-order phase transformation between spheres and cylinders and a reorientation from in-plane to out-of-plane cylinders occur during the annealing process. |
Monday, March 4, 2019 3:18PM - 3:30PM |
C49.00005: In-situ Observation of Non-solvent-induced Phase Separation of Cellulose Cuprammonium Solution by Small-Angle X-ray Scattering. Kazu Hirosawa, Tatsuhiro Iwama, Maiko Yamagata, Naoki Sakamoto, Ayumi Kurohara, Yoshiyuki Shiomi, Toru Morita Phase separation caused by permeation of non-solvents into polymer solution is called non-solvent-induced phase separation (NIPS). NIPS are often applied to fabrication processes of polymer materials such as wet-spinning of fibers and porous membranes. For example, NIPS of cellulose cuprammonium solution in water has been utilized to manufacture regenerated cellulose fibers. Hence, understanding the mechanism of NIPS has crucial importance in chemical industries. However, study of NIPS is challenging because it is complicated process which includes time-dependent variation of composition of polymer, solvent, and non-solvent molecules. To understand the structure formation mechanism, we performed in-situ structural analysis on NIPS process of cellulose in cuprammonium solution by means of small-angle X-ray scattering (SAXS). From time-development of SAXS profiles of the cellulose solution, we characterized phase separation structure and the dynamics of structural growth. Eventually, we clarified that network structure having ~ 10 nm characteristic length is formed by desorption of ammonia from cellulose solution into water. |
Monday, March 4, 2019 3:30PM - 3:42PM |
C49.00006: The Multi-Layered Structure of Novel Cellulose-Coated Oil-in-Water Emulsions Revealed by Contrast Variation Neutron Scattering Yachin Cohen, Sofia Napso, Dmitry Rein, Zhendong Fu, Aurel Radulescu Amphiphilic cellulose chains dissolve molecularly in the ionic-liquid 1-ethyl-3-methylimidazolium acetate. When the solution is mixed vigorously with oil and water a stable oil-in-water emulsion is formed, as water regenerates an amorphous cellulose coating on the oil droplets. Imaging by cryo-transmission electron microscopy indicated a unique multilayered structure of the cellulose coating. Small-angle neutron scattering from these emulsions was measured at three contrasts: full contrast (protiated oil and cellulose in D2O), shell contrast (oil matched to D2O) and core contrast (water matched to cellulose). The fitted model describes a spherical core with two concentric shells. The fitted parameters were the core diameter and thicknesses of the two shells, and the scattering length densities of the inner and outer shells, to account for their cellulose content. Particular attention was focused on whether the inner shell is imbibed by water or oil. It was concluded that the oil core (diameter 67±17 nm) is surrounded by a water-imbibed cellulose hydrogel (~3% cellulose), of thickness 34.5 nm an outer coating of a dense cellulose layer 3.5 nm thick. This novel structure may be utilized as a microreactor for cascade enzymatic reactions |
Monday, March 4, 2019 3:42PM - 4:18PM |
C49.00007: Probing chemical pathways in polyamide reverse osmosis membranes Invited Speaker: Alexandra Porter Reverse Osmosis (RO) membranes are widely used for sea water desalination applications. As the cost of installing desalination plants at sea is high it has become important to have a fundamental understanding of how the membranes work so that costs can be reduced. Much effort has gone into understanding the bulk properties of the membranes, but little effort on understanding then nanoscale interactions that control ion selectivity. The membranes are made from a polyester backing layer, a polysulfone (PSf) support and a polyamide (PA) membrane which is typically 100-500nm thick in a commercial membrane. Due to the membrane’s complex hierarchical structure, the controllability of ion selectivity remains unclear. |
Monday, March 4, 2019 4:18PM - 4:30PM |
C49.00008: Enzyme Immobilization in Mesoporous Metal-Organic Frameworks by SANS Lilin He, Xiaoliang Wang, Shuo Qian, Shengqian Ma Metal-organic frameworks (MOFs) are an emerging class of solid supports for enzyme immobilization owing to their high accessible pores and tunable pore size and surface for increasing affinity between enzymes and supports. Although the immobilization of enzymes by MOFs has shown improved catalytic efficiency, enzymes’ location in the hierarchical solid matrix, the relationship between enzyme dimension and pore size, and conformations of encapsulated enzymes remain elusive. In this work, we present a small-angle neutron scattering (SANS) characterization of cytochrome C (CyT. C) adsorbed into Tb-TATB under in-situ conditions. The scattering curve of unloaded Tb-TATB showed mass fractal feature arising from the network structure and a shoulder at ~0.03Å presumably corresponding to disordered building blocks or defects in the crystals. The correlation peaks located between 0.07 and 0.4 Å-1 were attributed to ordered arrangement of two nanopores, 39 Å and 47 Å, respectively. Upon loading of the CyT. C, substantial decreasing intensities of Bragg peaks proved the entry of enzyme molecules into the MOF’s cages with entry windows that are smaller than the enzyme. |
Monday, March 4, 2019 4:30PM - 4:42PM |
C49.00009: The Influence of Ionic Liquids on the Nanostructure of Polyimide based Aerogels Samantha J. Rinehart, Baochau N. Nguyen, Rocco P. Viggiano, Mary Ann B. Meador, Mark Dadmun Aerogels are promising materials for many aerospace applications, including high performance antennae and flexible insulation because of their inherent low density-high surface area properties. Polymeric aerogels, more specifically polyimide aerogels (PIA), provide excellent mechanical properties beyond traditional silica aerogels while maintaining the required thermal stability. NASA has investigated PIA paired with ionic liquids to develop novel mechanically robust electrolyte systems for next generation batteries. PIA surface area, porosity, and pore volume are important properties; however, these measurements are traditionally conducted sans solvent. Because of this, the impact of the ionic liquid on the nanoscale structure of PIA is unclear. To determine the impact of solvent presence, we use small angle neutron scattering to determine solvated PIA skeletal size and composition. Our results indicate that the pores as well as the polyimide skeleton absorb solvent. The amount of solvent uptake in the struts is dependent upon ionic liquid structure as well as polyimide structure. These results broaden the characterization of polymeric aerogels and provide the ability to correlate structural characteristics to their performance. |
Monday, March 4, 2019 4:42PM - 4:54PM |
C49.00010: Effect of Electrostatic Interactions Between Nafion and Functionalized Nanoparticles on Ionomer Morphology and Nanoparticle Dispersion Allison Jansto, Apoorva Balwani, Tyler Martin, Ronald Jones, Eric Davis Ionomer nanocomposites have emerged as a promising replacement to traditional polymer electrolyte membranes for technologies like vanadium redox flow batteries as they curtail undesired vanadium ion crossover while maintaining high proton conductivity. However, the mechanism by which the introduction of silica nanoparticles (SiNPs) acts to increase ion selectivity remains elusive. Presently, SiNP surface chemistry was systematically altered to determine the relationship between SiNP dispersion, membrane morphology, and vanadium ion transport, via transmission electron microscopy, small-angle neutron scattering (SANS), and ultraviolet-visible spectroscopy, respectively. Results indicate that the SiNP surface chemistry plays a vital role in controlling their dispersion and resultant ionomer morphology, where changes in SANS data were observed as a function of both surface chemistry and SiNPs loading in the ionomer membrane. Further, it was observed that the SiNP dispersion state had a direct impact on the vanadium ion permeation: SiNP aggregation reduced vanadium ion crossover as compared to well-dispersed particles with the same end functionality. Additionally, the overall NP surface charge is a key factor in controlling vanadium ion permeation through these composite membranes. |
Monday, March 4, 2019 4:54PM - 5:06PM |
C49.00011: Exchange Dynamics of Fluoroalkyl Block Copolymers in Selective Solvents Seyoung Kim, Yunshik Cho, Jee Hyun Kim, SooHyung Choi, Kookheon Char Due to omniphobic nature of fluoropolymers, block copolymers (BCPs) having fluoropolymer block can be an excellent choice for self-assembly of multi-compartmented nanoparticles. However, the strong incompatibility between fluoroblock and solvent could pose high energy barrier for the exchange of BCPs, kinetically trapping the systems. Herein, we investigated the chain exchange dynamics of the self-assembled fluoroalkyl-BCP micelles as well as their structures using contrast-varied small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS). Time-resolved SANS revealed the effects of temperature and fluoroblock length on the exchange dynamics within spherical micelles. Despite of high energy barrier for the fluoroblock pullout from the core domain, the exchange is reasonably fast due to significantly small friction within fluoropolymers. However, as the fluoroblock molar mass approaches 100 kDa, the energy barrier becomes tremendous that the fluoroblocks are actually arrested at the core. Therefore, the chain size of fluoroblock should be wisely chosen to drive self-assembly towards equilibrium in such strongly segregated systems. |
Monday, March 4, 2019 5:06PM - 5:18PM |
C49.00012: Phase behavior of poly(9-(4-vinylbenzyl)adenine)-block-polystyrene copolymers Eunseol Kim, Avnish Kumar Mishra, Chungryong Choi, Mooseong Kim, Seungkyoo Park, Soyeong Park, Seonghyeon Ahn, Jin Kim In this study, we successfully synthesized adenine-containing block copolymers, poly(9-(4-vinylbenzyl)adenine)-block-polystyrene (PVBA-b-PS), using reversible addition-fragmentation chain transfer (RAFT) polymerization and characterized them by size exclusion chromatography, and nuclear magnetic resonance spectroscopy. |
Monday, March 4, 2019 5:18PM - 5:30PM |
C49.00013: Order-order transition in gyroid forming block copolymer in thin films. Cindy Gomes Correia, Karim Aissou, Georges Hadziioannou, Christophe Navarro, Guillaume Fleury Block copolymers provide an attractive route for the definition of well-defined nanostructures. Intense efforts are currently being devoted for their directed self-assembly to extend the performances of conventional lithography. Consequently, we have designed polycarbosilane-based block copolymers that are suitable for next-generation lithography thanks to the high segregation strength and the high etching contrast provided by the Si-containing block1. Here, we chose to focus on the gyroid phase, as it has shown potential for 3D complex-ordered structures. We present a study on the self-assembly of thermally-annealed gyroid films. We demonstrate a transition from the (211) plane of the gyroid oriented parallel to the free surface to in-plane cylinders with increasing annealing time. This transition was correlated to the evaporation of the remaining solvent in the film during the annealing process, thus driving the mesostructure towards the cylindrical window of the phase diagram. The morphological assignments were confirmed using SAXS measurements in bulk as well as AFM and GISAXS characterizations in thin film. Such gyroid could be used in nanotechnologies as templates for bulk heterojunction solar cells or as filtration membranes. |
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