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 AAA03: V: Self-Assembly and Composite Materials |
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Sponsoring Units: DSOFT Chair: Debashish Mukherji, University of British Columbia Room: Virtual Room 3 |
Wednesday, March 22, 2023 12:30PM - 12:42PM |
AAA03.00001: Electric-field distributions from densest packings of charged spheres in cylindrical confinement Yanyu DUAN, Zecheng Gan, Ho-Kei CHAN Identical hard spheres in cylindrical confinement exhibit a variety of densest-packed columnar structures that vary with the corresponding cylinder-to-sphere diameter ratio D. Research in the past two decades has focused on the structural characteristics of such structures, and less attention has been paid to their physical properties. We have investigated theoretically the electric-field distributions from five types of such structures at D ∈ [1, 2], namely linear chain, planar zigzag, single helix, double helix, and achiral doublets, where each structure of interest is modelled as a spatial distribution of identical point charges at the sphere centers. For increasing radial distance, we observed a transition from a near-field distribution that depends sensitively on the micro-arrangement of particles, to a far-field limit that is equivalent to the electric-field distribution from a continuous line of charge, as quantified by a variation in the scaling behavior of the radial electric field. Our findings may open up new avenues for generating specific electric-field distributions through the manipulation of micro-arrangements of charged particles in quasi-one-dimensional confinement. |
Wednesday, March 22, 2023 12:42PM - 12:54PM |
AAA03.00002: Topological Defects with Tunabel Chirality and Morphology Induced by 3D-Printed Square Networks Zhongjie Ma, Shengzhu Yi, Rui Zhang, Qi-Huo Wei Topological defects exist widely in the orientationally ordered matter such as nematic liquid crystal. Their morphphology and topological properties can be controled by topology and anchoring conditions of their boundaries, Here we used two photon printing technique to make microscale square networks and study topological defects they induce in nematic liquid crystals. We found that when the substrate distance increases from 2.5 μm to 20 μm, the induced topological defects change from a -1/2 disclination loop to a hyperbolic defect located at the center, and ultimately transform into off-entered point defects. In the hyperbolic defect case, a chiral twist is emergent in central area. We found that the twist of the chiral areas can be fine tuned by an external electric field. By using the Landau-De Gennes theory, we explored how the boundary conditions influence on topological defects morphology and free energy. The simulation results yielded good agreement with the experiment observations. Further, we found that the chirality of the central adrea can be predesigned by introducing slight chirality in the squares networks. |
Wednesday, March 22, 2023 12:54PM - 1:06PM |
AAA03.00003: Phase separation of nonionic polymers that can stick and slide Amal Narayanan, Apoorva Vishwakarma, Ali Dhinojwala, Abraham Joy The molecules with a propensity to undergo liquid-liquid phase separation (LLPS) form two distinct liquid-like phases known as dense and dilute phases. The dense phase formed from LLPS has unique characteristics such as a density higher than water, low viscosity, and low underwater interfacial tension. These distinct features facilitate the use of dense phases as scaffolds for drug delivery, tissue adhesive, and protein encapsulant. Most synthetic systems that undergo LLPS are created by complexing oppositely charged polymers. The formation of a dense phase from complexation requires careful tuning of the molar ratios of oppositely charged polymers, maintaining the correct pH and ionic strength. The instability of charged polymers to external factors and their potential cytotoxicity can hinder the use of such multicomponent complexed dense phases in dynamic wet environments with fluctuations in pH and ionic strength. Here we discuss, a tropoelastin-inspired design of synthetic nonionic polymers (HyPPos) that undergo single-component LLPS above their lower critical solution temperature. The phase separation behavior of these polymers is insensitive to the changes in pH. Using HyPPos, we studied the minimal physicochemical parameters required for the synthesis of the polymers that undergo single-component LLPS. We show that the designed polymers can be engineered to hydrolytically degrade, stick underwater, and displace selective biofilms submerged underwater. |
Wednesday, March 22, 2023 1:06PM - 1:18PM |
AAA03.00004: Designing Self-Limiting Assembly Using Magnetically Interacting Micro-Panels Remi Drolet, Chrisy Xiyu Du, Ella M King, Agnese Curatolo, Zexi Liang, Melody X Lim, Itai Cohen, Paul L McEuen, Michael P Brenner Magnetic handshake materials is a newly developed materials platform for programmable self-assembly. This platform enables highly specific interactions to be easily printed in complex structures and arrangements, revealing a vast potential design space for micron-scale magnetic structures and machines. Since the design space for building block design is so large, having theoretical and computational approaches is crucial to the rapid design of materials with desired structures and functions. In this talk, we introduce a theory-computation-experiment workflow to design building blocks for targeted assembly behaviors. Of particular interest are 2-dimensional square panels. These constitute a simple building block that is capable of self-assembly into various structures, such as larger 2-by-2 squares, depending on the arrangement of constituent dipoles. Firstly, we validate the yield prediction from a statistical mechanics informed theoretical model by running molecular dynamics simulations. Secondly, we show how to use the theoretical model to design interactions for hierarchical assembly into structures of increasing size. Lastly, we demonstrate the possibilities of translating our designs into experimental realizations. |
Wednesday, March 22, 2023 1:18PM - 1:30PM |
AAA03.00005: Thermal transport in amorphous and semi-crystalline epoxy networks via bond engineering Debashish Mukherji Thermal transport coefficient (k) is an important property of condensed systems, where establishing microscopic understanding is extremely important for their possible uses under extreme environmental and practical conditions. Here polymers are an important class because they provide different pathways for energy transfer. For example, the heat flow between |
Wednesday, March 22, 2023 1:30PM - 1:42PM |
AAA03.00006: 3D Crystals of Supramolecular Nanotubes Containing up to 94% of Liquid Water Goran Ungar, Ningdong Huang 3D crystalline order with 1 nm resolution is observed in aqueous solutions of supramolecular nanotubes at concentrations as low as 6 wt%. The nanotubes are self-assembled from ionic star-like mesogens with three oligobenzamide branches. 50 such molecules arrange radially into supramolecular rings which, in turn, stack on top of each other to form long hollow tubes with 15 nm outer diameter. X-ray based electron density maps and cryo-TEM show that parallel nanotubes arrange on a perfect hexagonal lattice, with interaxial separation up to 25 nm and surface-to-surface water gap up to 10 nm, depending on concentration. Unexpectedly, fiber diffraction on sheared solutions feature numerous hkl Bragg reflections on several layer lines. These indicate longitudinal interlock between the tubes and 3D crystalline order with molecular-scale detail transferred over long distance water. Increasing concentration brings slowing tube dynamics as probed by X-ray photon correlation spectroscopy. The tubes are non-centrosymmetric. The observed high 3D order can be understood in terms of long-range attractive forces between like-charged tubes and the extremely high intra-tube correlation length. |
Wednesday, March 22, 2023 1:42PM - 1:54PM |
AAA03.00007: Novel smart materials from Pluronic F127 and akaganeite (β-FeOOH) nanorods Surya Narayana N Sangitra, Ravi Kumar Pujala Hydrogels are soft materials with a 3D internal network-like structure with water as a significant component. The word "smart" corresponds to a direct response to changes in environmental conditions like pH, light, pressure, temperature, and electric and magnetic fields. To develop simple, cost-efficient, and biocompatible hydrogels with multiple stimuli-responsive behaviours, we made novel smart material (thermoresponsive hydrogels) consisting of akaganeite (β-FeOOH) nanorods and pluronic F127 (PF127). Though akaganeite has been used as a precursor to preparing stable iron-oxide states (e.g., hematite and magnetite), the studies on nanorods to be used as the main component in hydrogels are at the nascent stage. This talk presents a detailed methodology of akaganeite nanorod synthesis by a simple sol-gel process. XRD, spectroscopy, electron microscopy, and light scattering experiments characterize its properties. A phase diagram and thermoresponsive behaviour based on rheological experiments with flow curves, amplitude and frequency sweep are established for 20 wt% PF127 with low concentrations (0.1- 0.1 wt%) of β-FeOOH nanorods. Finally, a plausible physical mechanism is proposed to fundamentally understand how and why this unique responsive behaviour appears based on different interactions in the nanocomposite system. |
Wednesday, March 22, 2023 1:54PM - 2:06PM |
AAA03.00008: Computer simulations of melts of ring polymers with non-conserved topology: A dynamic Monte Carlo lattice model Mattia Alberto Ubertini, Angelo Rosa We develop a kinetic Monte Carlo scheme for polymer chains on the 3d FCC lattice which takes into account the possibility for pairs of polymer strands to perform strand crossing at a given tunable rate. We apply this method to melts of ring polymers and we characterize their structure and dynamics. We focus on the complex topology arising during the relaxation process by looking, in particular, at the formation of knots, links and higher order topological structures. As for the dynamics, we show that strand crossing makes polymers to diffuse faster with respect to melts of unknotted and non-concatenated rings provided that the time-scale of the process is smaller respect to the relaxation time of the unperturbed state, in agreement with recent experiments employing solutions of DNA rings in the presence of the type II topoisomerase enzyme. In contrast, at slow rates the melt is shown to become slower, and this prediction may be easily validated experimentally. |
Wednesday, March 22, 2023 2:06PM - 2:18PM |
AAA03.00009: Entropy-driven crystallization of flexible chains of hard spheres under confinement Daniel Martínez-Fernández, Pablo M Ramos, Miguel Herranz, Katerina Foteinopoulo, Nikos Karayiannis, Manuel Laso Through extensive Monte Carlo simulations, we study the heterogeneous crystallization of linear, fully flexible chains of tangent hard spheres under confinement in one or three dimensions. Confinement is realized through the presence of flat, impenetrable, and parallel walls. The phase behavior is studied by employing a wide range of systems with varied average chain lengths and packing densities. For that, crystal nucleation and growth are analyzed through the Characteristic Crystallographic Element (norm) descriptor. The phenomenon is naturally split into two distinct contributions: surface crystallization on the walls, and bulk crystallization far from them. Depending on the simulation conditions, different morphologies are established in the bulk zone ranging from random hexagonal close-packed layers with a unique stacking direction, perpendicular to the walls (confinement in one dimension) to predominantly hexagonal close-packed (confinement in all dimensions) crystals. In parallel, surface crystals show perfection with a predominantly triangular character. Finally, we analyze the entropic origins of the phase transition and identify the similarities and differences with respect to the bulk, homogeneous crystallization. |
Wednesday, March 22, 2023 2:18PM - 2:30PM |
AAA03.00010: Colloidal molecules with directionality and controlled flexibility Daniela J Kraft
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