Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session A15: Advances in Polymer Physics |
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Sponsoring Units: DPOLY Chair: Janani Sampath, University of Florida Room: Room 207 |
Monday, March 6, 2023 8:00AM - 8:12AM |
A15.00001: Thermodynamic and Conformational Analysis of Chiral Block Copolymers in the Disordered State Michael J Grant Block copolymers with one chiral block have emerged as promising candidates for materials with novel properties like photonic bandgaps and negative refractive index. Thermodynamic insights into the self-assembly of these materials is of great interest as it would allow more facile access to these highly desirable materials. Experimental studies attempting to understand the self-assembly of these chiral polymers have yielded intriguing results – despite identical structural properties of the chiral lamellar structure, the chiral molecules exhibit a decrease in the order-disorder temperature when compared to the achiral counterparts. Thus, altering the molecular shape alters the entry point of these novel phases possessing sought after properties. Employing a combination of free energy perturbation and thermodynamic integration in a particle-based simulation model, we are able to quantify the free energy, entropy, and enthalpy to yield a highly accurate quantification of these unresolved thermodynamics by measuring the effects of increasing the chirality of one block in the block copolymer melt. When tying these contributions with varying topology metrics two distinct regimes were found - a compressed regime which corresponds to recent discussions in the literature, and a novel elongated regime.The insights generated from this study suggests that the development of new chiral materials in the elongated regime could exhibit novel mechanical properties. |
Monday, March 6, 2023 8:12AM - 8:24AM |
A15.00002: Structure Determination in Bulk Films of Two-Dimensional Covalent Organic Frameworks Frederick L Beyer, David McLeod, Eric D Wetzel, Emil J Sandoz-Rosado Two-dimensional covalent organic framework materials (2D COFs) are being studied for their potential to act as porous, high-surface-area host structures for catalysts and sensors, and as functional membranes in energy storage devices, water filters, chemical separators, etc. A key requirement for achieving the desired chemical, physical, and mechanical properties in these films is the formation of a well-ordered framework structure as dictated by the functionality and stoichiometry of the component monomers. However, the bulk organization of the individual 2D macromolecules into larger ensembles will also certainly play an important role in determining the final properties. In this work, bulk films made from trifunctional 1,3,5-tris(4-aminophenyl)benzene (TAPB) and difunctional terephthaldehyde (PDA) are interrogated using combined small-angle and wide-angle X-ray scattering. This technique provides information not only on the hexagonal lattice structure of the 2D COF, but also on the stacking of the individual 2D molecules and the overall size and orientation of the ensembles. X-ray scattering combined with in situ heating provides insight into the stability of the crystalline ensembles as well. Current results on this effort will be presented. |
Monday, March 6, 2023 8:24AM - 8:36AM |
A15.00003: 3D Imaging, Molecular Modeling and Graph Theory of Polyamide Membranes with Interconnected Networked Crumples Reveal Insights on Morphogenesis, Separation Performance and Mechanical Properties Falon C Kalutantirige, Qian Chen Polyamide (PA) membranes serve as an active layer in thin-film composite (TFC) membranes used for organic solvent separation. Despite the wide use of TFC membranes, there is little understanding of morphogenesis of the irregular interconnected networked crumple-like 3D nanomorphology of the PA active layer, and its impact on separation and mechanical properties of the membrane. Adopting a multifaceted approach of 3D imaging, morphometry and modeling using low-dose electron tomography, atomic force microscopy (AFM) and coarse-grain (CG) simulations, we present molecular insights into the nanomorphogenesis of networked PA membranes and relate their organic solvent permeabilities and moduli to the 3D nanomorphology. We explore the 3D nanomorphology of three PA membranes with interconnected networked crumples to relate methanol permeance to 3D morphological parameters such as void volume and local membrane thickness. We use CG simulations and 3D thickness mapping to support a coalescence and growth mechanism of membrane morphogenesis. Applying skeletonization to simplify the 3D volume of PA membranes, we quantify the networked PA membranes using graph parameters of network density and efficiency, thereby relating the nanomorphology to the apparent modulus measured by AFM. |
Monday, March 6, 2023 8:36AM - 8:48AM |
A15.00004: Organic Thin Film Transistor Based on the Organic-Inorganic Hybrid Ferroelectric Insulator Layer Hyowon Jang, Yongju Lee, SWARUP BISWAS, Hyeok Kim Flexible memory technologies that work in a variety of environments are now necessary due to the increased interest in flexible semiconductors and flexible displays. We employed a poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] thin film insulator layer with piezoelectricity, superconductivity, and ferroelectricity capabilities in this application. However, because P(VDF-TrFE) is a semi-crystalline polymer, leakage current arises due to crystal defects and a fragile film morphology. So, we attempted to reduce leakage current value using a hybrid structure with inorganic insulator silicon dioxide (SiO2), and formed a complementary organic/inorganic hybrid ferroelectric insulation layer-based organic thin film transistor that minimizes leakage current value while maximizing ferroelectric characteristics via SiO2 thickness control (17nm, 42nm, 100nm, 300nm). As a consequence, it was found that the SiO2 100nm and P(VDF-TrFE) 200nm organic/inorganic hybrids had the highest hysteresis characteristics, and the transistor device characteristics were also extremely excellent. |
Monday, March 6, 2023 8:48AM - 9:00AM |
A15.00005: Effect of shape and alignment of carbon-based nanofillers on quantum tunneling effect of triboelectric nanogenerators Mina Shanbedi, Alamgir Karim, Haleh Ardebili Triboelectric nanogenerators (TENGs) have received recent interest in converting unconventional mechanical energy to electricity, particularly as a sustainable form of energy generation from sources such as wind and friction. Energy conversion in TENGs is based on triboelectrification and electrostatic induction effects. However, its output electrical characteristics still need more fundamental investigation and development. Based on equations, increasing the triboelectric polymer dielectric constant should enhance the charge density and lead to higher current density and voltage by facilitating charge transfer from the contact surface toward electrodes. Nanoparticles can enhance charge transfer in TENGs by increasing the polymer matrix's dielectric constant, especially when their concentration approaches the percolation threshold. However, the maximum dielectric constant around the percolation threshold does not track the maximum electrical performance of the TENG device. The shape, and orientation of anisotropic nanoparticles, also play a role in the outcome of the polymer's dielectric constant. This research investigates the effect of carbon-based nanoparticles on PDMS nanocomposite/aluminum TENG output, considering the aforementioned factors. The particles are chosen from various molecular shapes and dielectric constants, including carbon black (CB), multiwall carbon nanotube (CNT), graphene oxide (GO), and reduced graphene oxide (r-GO). Here we show the optimum filler weight fraction for maximum voltage and current usually differs from the concentration for the highest dielectric constant near the percolation threshold, due to the quantum tunnel effect. Here we show that the gap between the concentration with the highest triboelectric performance and the concentration with the highest dielectric nanofillers depends on the shape and angle of the nanofillers in the device. |
Monday, March 6, 2023 9:00AM - 9:12AM |
A15.00006: Fracture behavior of elastomers: a new look into phenomenology known for over six decades Shi-Qing Wang, Zehao Fan For plastics we have advanced a scaling level molecular description of yielding and brittle-ductile transition.1, 2 In contrast polymer physics has not really gone beyond the classical formulation of rubber elasticity for crosslinked polymers because of the lack of structural characterization of the network. A long-standing question is why elastomers seem to have rather “low” tensile strength. On the other hand, the same elastomers are known3 to show improved tensile strength under higher rate of drawing. Separately, toughness (i.e., critical energy release rate) is found to grow sharply with the rate, which has been interpreted as due to increased energy dissipation.4 We apply time-dependent, spatially resolved polarized optical microscopy to further investigate the phenomena. |
Monday, March 6, 2023 9:12AM - 9:24AM |
A15.00007: Multifunctional coatings made of extremely confined molecular and polymeric glasses Cindy Chen Molecular or polymeric glasses can be placed under extreme nanoconfinement when infiltrated into self-assembled nanoparticle (NP) films. The properties of this new class of nanocomposites can be controlled through NP size and shape, as well as the chemical composition of the glass and NP, thus serving as promising scalable materials for multifunctional coatings and membranes. Here, we investigate the thermal- and photo-stability of these materials and demonstrate their improved bonding as adhesive layers. Molecular nanocomposites made of indomethacin (IMC) molecule in silica NPs show a Tg increase of ~ 30 K upon confinement in ~ 3 nm pores, which corresponds to a factor of ~ 10 slow-down of thermal degradation rate and increased activation energy for degradation at elevated temperatures. Photodegradation rates of this material under both low O2 and ambient conditions is also improved. In polymeric systems, the highly confined nanocomposite can be used as a bonding layer for glass to polymer adhesion. We show that the adhesive strength is dramatically improved when polystyrene (PS, 885 kg/mol) is confined in silica NPs. Enhanced adhesion is more pronounced with decreasing NP layer thickness and increasing molecular weight. These findings provide insight into the behavior of confined polymers and small molecules and will guide the development of robust functional coatings with high NP loading when improved mechanical and thermal/photo properties are desired, or when gas diffusion needs to be limited. |
Monday, March 6, 2023 9:24AM - 9:36AM |
A15.00008: In-situ investigation of self-assembled block copolymer nanostructural evolution during sulfonation-based crosslinking Anthony Griffin, Mark Robertson, Paul Smith, Alejandro Guillen-Obando, Zhe Qiang Block copolymer (BCP) self-assembly provides a facile, low-cost method for developing intricate, well-ordered nanostructures with several applications, such as the synthesis of ordered mesoporous carbon (OMC). We have demonstrated the heterogeneous, sulfonation-based crosslinking of a triblock copolymer, polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, for OMC synthesis, where crosslinking and nanostructural rearrangement occur simultaneously. This talk will present a systematic, in-situ study to develop fundamental understanding on the nanostructure evolvement during crosslinking, where a rich interplay between domain rearrangement and kinetic morphology trapping determines the final self-assembled nanostructure. Specifically, in-situ small-angle x-ray scattering (SAXS) will be employed to probe how sulfonation temperature and time affect domain spacing and degree of ordering. The morphological development of SEBS during crosslinking will be corresponded with their chemical transformation kinetics throughout the reaction. A relationship between sulfonation conditions and BCP self-assembly was established, providing opportunities for developing a process-tunable platform for intricate nanostructure control in ordered porous materials. |
Monday, March 6, 2023 9:36AM - 9:48AM |
A15.00009: Modulating Solution Phase Behavior through Block-Random Copolymer Sequence Lauren W Taylor, Rodney Priestley, R. A Register Monomer sequence in synthetic and biological soft matter has been shown to play a critical role in material phase behavior. Recent work has used coarse-grained molecular simulations to demonstrate that small changes in sequence of intrinsically disordered proteins at fixed composition, particularly at the end of the chain, can profoundly impact the liquid-liquid phase separation of these molecules. Here, anionic polymerization was used to synthesize styrene-isoprene copolymers with similar molecular weight, polydispersity, and overall composition (50/50 wt% of styrene/isoprene) but small changes (5-10%) in monomer sequence. The sequence was altered by placing blocks of polystyrene (PS) or polyisoprene (PI) at the end or in the middle of a random copolymer chain. Dynamic light scattering was used to study the phase behavior in n-hexane. A PI block at the end of the chain significantly lowers the critical temperature (Tc) and promotes the formation of very large (100 nm) stable micelles prior to and after macroscopic liquid-liquid phase separation. Conversely, a PI block in the center of the chain increases the Tc. When the short blocks are PS, the effect is opposite and more pronounced; a block at the end of the chain increases Tc and a block in the center decreases Tc. Finally, for blocks of both PS and PI, the shift in Tc is larger when the block is placed at the end of the chain, in qualitative agreement with simulations. |
Monday, March 6, 2023 9:48AM - 10:00AM |
A15.00010: Weak magnetic fields induce anomalous disorder-to-order transitions in spherical block copolymer micelle solutions Michelle A Calabrese, Grace V Kresge While block copolymers (BCPs) are promising materials due to their tunable structure and functionality, practical methods for processing BCPs with controlled grain size and orientation remain challenging. We recently discovered anomalous magnetic field-induced disorder-to-order transitions in weakly diamagnetic, coil-coil BCPs that cannot be explained by traditional mechanisms of domain alignment. While prior work on field-directed BCP assembly focused on alignment of a structure with inherent anisotropy, here stable ordered phases rapidly form during magnetorheology measurements (B ≤ 0.5 T) on low viscosity solutions of geometrically-isotropic, disordered BCP micelles; this phenomena is accompanied by an up to six order-of-magnitude increase in modulus. Via small angle neutron and X-ray scattering, we demonstrate that weak magnetic fields induce formation of highly ordered phases typically observed in analogous non-magnetized solutions at higher polymer concentrations. At early magnetization times, BCPs form face-centered (fcc) and body-centered (bcc) cubic packings composed of spheres with a lower aggregation number than those that form at zero-field conditions. With increasing magnetization time, new order-to-order transitions are identified, including transitions between cubic packings and hexagonally-packed cylinders (fcc->bcc->cyl). Fourier transform infrared spectroscopy suggests that the increase in per-chain interfacial area resulting during these ordering transitions is likely driven by both changes in corona-solvent interactions and in chain conformation induced by the applied field. Fully understanding this anomalous assembly phenomena will afford access to BCP structures and associated lengthscales inaccessible via traditional routes, and will provide a platform for developing well-ordered BCP materials under mild processing conditions. |
Monday, March 6, 2023 10:00AM - 10:12AM |
A15.00011: Solution Self-assembly of T-shaped Sphere-Rod Rigid "Block Copolymers" into Strictly defined Onion-like, Possible Liquid Crystalline Structures Yifan Zhou, Jiancheng Luo, Jingfan Wei, Tao Wen, Stephen Z Cheng, Tianbo Liu A series of T-shaped sphere-rod amphiphilic macromolecules are studied to reveal the self-assembly behaviors of rigid block copolymers. The hydrophilic polar group is composed of Keggin, Anderson, or Dawson type of polyoxometalate (POM) clusters, linked with the hydrophobic domain in a T-shaped way. Onion-like spherical structures with multiple concentric layers are formed in the water/acetonitrile mixed solvents of Keggin T-shape-linked oligo fluorene (Keggin-TOF4). Amazingly, the interlayer distance is strictly constant for different layers, and it does not change with the external coniditions. Instead, the assemblies respond to external changes by changing their total number of layers. Interestingly, in the mixture of two hybrid macromolecules with different polar head groups (Anderson-TOF4 and Dawson-TOF4), they can accurately self-recognize with each other by forming individual assemblies instead of mixed ones. An interdigitation model, supported by 2D-NMR, is proposed to explain how the rigid amphiphiles pack and assemble into highly ordered onion-like structures. The counterion-mediated attraction between charged hydrophilic clusters is expected to play an important role in the inter-layer attraction. Overall, the size, shape, charge, and specific geometry of rigid building blocks lead to the unique final assembled structures. This study demonstrated that block copolymers with fully rigid domains possess completely different assembly rules from common block copolymers. |
Monday, March 6, 2023 10:12AM - 10:24AM |
A15.00012: Encapsulation of phenylacetic acid in polymeric nanoparticles during polymerization induced self-assembly Guanrui Li, Ralm Ricarte, Daniel Barzycki Amphiphilic block copolymer nanoparticles (PNPs) can behave as drug carriers for hydrophobic drugs. Polymerization induced self-assembly (PISA) is a versatile and efficient method for synthesizing PNPs. For PISA conducted in the presence of a drug, the polymerization, self-assembly, and drug encapsulation occur simultaneously. This approach simplifies synthesis and avoids the use of toxic organic solvents. The mechanism of drug encapsulation during PISA, however, remains an open question. Here, we investigate how encapsulation during PISA affects PNP structure and drug sequestration. The model block copolymer was poly(glycerol monomethacrylate)-b-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA). The model drug was phenylacetic acid, whose water solubility is 16 mg/mL. The nanostructure was characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Encapsulation efficiency was quantified using a combination of DLS and 1H nuclear magnetic resonance diffusion-ordered spectroscopy (NMR DOSY). With increasing concentration of the drug and PHPMA degree of polymerization (NPHPMA), the PNP morphology shifted from spherical micelles to cylindrical micelles to vesicles. At a targeted drug loading of 32 mg/mL, the encapsulation efficiency reached a maximum of ~ 75%. Increasing NPHPMA changed the nanostructure but minimally altered encapsulation efficiency, suggesting that the drug may be partitioning into the hydrophilic corona. |
Monday, March 6, 2023 10:24AM - 10:36AM |
A15.00013: Atomistic modeling of hydration and antibiofouling of TMAO-polymer surfaces Pranab Sarker, Grace T Chen, Md Symon J Sajib, Nathan W Jones, Tao Wei Trimethylamine N-oxide (TMAO)-derived zwitterionic polymers have emerged as a next-generation sustainable material for avoiding biofouling on submerged surfaces in marine and biomedical applications. However, the underlying interactions between TMAO surfaces and proteins at the microscopic level remain unclear. We performed atomistic molecular dynamics simulations coupled with free-energy computations to provide insights into the hydration of TMAO-polymer brushes (pTMAO) and their interactions with proteins in pure and saline water. Our simulations show a condensed hydration water layer on the pTMAO surfaces, even in the presence of salt. The free energy calculations further quantify a smaller protein desorption energy for the pTMAO surfaces. However, their surface's hydration is strong enough to resist protein adsorption, upon creating an energy barrier, compared to other biofouling surfaces. Even the presence of salts has a negligible effect on their ability to resist protein adsorption. Our work thus provides a thorough understanding of hydration, protein adsorption, and anti-biofouling behavior of TMAO-derived polymer brushes. |
Monday, March 6, 2023 10:36AM - 10:48AM |
A15.00014: Manipulating block copolymer morphology and self-assembly behaviors through sulfonation-induced crosslinking Mark Robertson, Paul Smith, Alejandro Guillen-Obando, Anthony Griffin, Zhe Qiang Block copolymer self-assembly is indispensable for establishing well-ordered nanostructures in polymer materials. Furthermore, the ability to manipulate these nanostructures and their derived functional materials can enhance their performance in many applications. Specifically, ordered mesoporous materials can be fabricated through converting block copolymer morphologies into tailored pore textures, and greatly benefit from the wealth of accessible morphologies. This work demonstrates the morphological evolution of a triblock copolymer system, and its implications, as it undergoes a heterogeneous crosslinking reaction in the solid state for the preparation of mesoporous materials. The morphology established during this process is the result of an intricate interplay between separate reactions within the majority and minority phases of the block copolymer and directly impacts the final structure of the porous material product. An in-depth understanding of the physical consequences that result from simultaneous crosslinking and swelling could provide a platform for the manipulation of self-assembly behaviors in the solid-state for block copolymer-derived materials. |
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