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 F02: Polyelectrolyte Complexation IFocus Live
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Sponsoring Units: DPOLY DSOFT Chair: Samanvaya Srivastava, University of California; Debra Audus, National Institute of Standards of Technology |
Tuesday, March 16, 2021 11:30AM - 11:42AM Live |
F02.00001: Structure, dynamics, and phase behaviors of novel quasi-coacervate gel composites Di Jia, Murugappan Muthukumar Traditional coacervates are dense liquid states composed of oppositely charged macromolecules formed via liquid-liquid phase separation. Here we report a novel system where charged macromolecules can simply complex with oppositely charged monomers to induce phase separation. Rich phase behaviors can be induced by tuning various parameters such as salt concentration and charge stoichiometry. When the charges of the monomers are more than the charges on the polymers, by tuning the salt concentration, there are three phase regimes. At low salt concentration, it is a phase-separated system; at high salt concentration, it is a one phase region where chains have single chain conformation. However, at intermediate salt concentration, there is an “emulsion suspension phase”, which contains stable self-assembled micelle-like structures with uniform size. More interestingly, in addition to the charged monomers, by adding extra neutral monomers and initiator, we can make gelation in the “emulsion suspension phase” so that the micelle-like structures can be trapped inside the gel mesh to function as “nanoreactors”. Such novel quasi-coacervate gel composites are complementary to the traditional coacervate systems. |
Tuesday, March 16, 2021 11:42AM - 11:54AM Live |
F02.00002: Modeling phase behavior of polyelectrolyte complex coacervates using simulations Sai Vineeth Bobbili, Scott Milner When oppositely charged polymers mix in aqueous solution, associative phase separation gives rise to coacervates. Experiments reveal the phase diagram for such coacervates, and determine the impact of charge density, chain length and added salt. Simulations often use hybrid MC-MD methods to produce such phase diagrams, in support of experimental observations. We propose an idealized model and a simple simulation technique to investigate coacervate phase behavior. |
Tuesday, March 16, 2021 11:54AM - 12:30PM Live |
F02.00003: Charge density and solvent effects on polyelectrolyte complexation Invited Speaker: Matthew Tirrell The fundamental polymer physics of polyelectrolyte complexation have been clarified substantially in recent years. However, the handles for tuning the phase behavior amd properties of polyelectrolyte complexes are numerous, every bit as large as the tuning of copolymer properties governed by van der Waals interactions. Thhis talk will present our studies on changing the solvent quality and the linear charge density along the chains in such complexes. Large, qualitative changes in the structure and properties of the complexes can be induced by both variables. |
Tuesday, March 16, 2021 12:30PM - 12:42PM Live |
F02.00004: Dynamics of Polyelectrolyte Complex Coacervates: A Molecular Dynamics Study Heyi Liang, Artem Rumyantsev, Phillip Rauscher, Juan De Pablo Polyelectrolyte complex coacervates (PECCs) are formed by mixing oppositely charged polyelectrolytes. While it is observed experimentally that adding salts to coacervates accelerates their dynamics, the underlying mechanisms remain elusive since the addition of salts often leads |
Tuesday, March 16, 2021 12:42PM - 1:18PM Live |
F02.00005: Concentration and separation of proteins using polyion condensates Invited Speaker: Saskia Lindhoud When oppositely charged macromolecules are mixed in aqueous systems at the right conditions, i.e., ionic strength, mixing ratio, pH, etc., solutions phase separate in a condensed phase which is rich in macromolecules and a dilute phase. The so formed polyion condensate can be liquid-like or solid-like. In both cases proteins can be captured in the condensate phase. This protein partitioning strongly depends on the ratio between the oppositely charged macroions. |
Tuesday, March 16, 2021 1:18PM - 1:30PM Live |
F02.00006: Biomacromolecules in Ternary Complex Coacervates Whitney Blocher McTigue, Jeanne Hardy, Sarah Perry Vaccines and other therapeutic cargo are made, transported, and stored along a “cold chain,” a system designed to maintain the refrigeration of these fragile cargos. To combat this, methods for decreasing the reliance of these cargos on the cold chain have garnered attention, with many efforts focusing on encapsulation strategies. Our work focuses on complex coacervation as an all-aqueous encapsulation strategy. Complex coacervation is a liquid-liquid phase separation phenomenon dominated by electrostatic interactions and entropy. We investigated the use of a two-polymer coacervate system for protein encapsulation to facilitate the incorporation of weakly-charged protein cargo and explored the incorporation of three model proteins as a function of solution conditions, polymer properties, and distribution of charges on the proteins. We determined that the net charge and distribution of charges on both the protein and polymers dominated protein incorporation, and confirmed this by comparing the incorporation of two variants of caspase-6 that differ in a critical charged patch. Our results have shown the encapsulation of caspase-6 almost doubled in the level of partitioning when displaying a charge patch. |
Tuesday, March 16, 2021 1:30PM - 1:42PM Live |
F02.00007: Complexation of two oppositely charged Polyeletrolyte chains: Role of entropy and enthalpy Soumik Mitra, Arindam Kundagrami We report a study of the complexation process of two oppositely charged polyelectrolyte (PE) chains in dilute solution interacting through screened Coulomb potential. The two PE chains, as well as the neutral complex, are considered to be hypothetical spheres whose radii quantitatively denote the sizes of the respective chains, and the system is characterized by its free energy, calculated within the uniform spherical expansion approximation. A comparison of the entropy gain of counterions freed due to complexation and enthalpy change due to the reorganization of ion-pairs of two types-the monomer-counterion and oppositely charged monomer-monomer identifies the entropy to be the major driving force for the process. Addition of salt weakens the drive for complexation. The free energy of the complex is monotonically downhill at modest physical conditions. |
Tuesday, March 16, 2021 1:42PM - 1:54PM Live |
F02.00008: Associative Phase Separation in Polyelectrolyte Complex Coacervates Yuanchi Ma, Vivek M Prabhu, Samim Ali, Yimin Mao
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Tuesday, March 16, 2021 1:54PM - 2:06PM Live |
F02.00009: General trends in the structure and phase behaviour of polyelectrolyte-nanoparticle assemblies Advait Holkar, Jesse Toledo, Samanvaya Srivastava Aqueous mixtures of oppositely charged polyelectrolytes (PE) and nanoparticles (NP) self-assemble into dense complexes. This self-assembly forms the basis of diverse phenomena ranging from flocculant action in water treatment, where the PE-NP flocs phase separate and sediment, to DNA compaction around histone proteins into chromatin. Factors such as the PE concentration, length, architecture and concentrations; NP charge, morphology and concentrations; and solution conditions (pH and ionic strength) play key roles in directing these PE-NP assemblies. In this presentation, we will delineate fundamental investigations into the phase behavior and structure of polyelectrolyte-NP assemblies using small angle X-ray scattering, turbidimetry and rheology with systematic variation of PE sizes and flexibility, NP sizes, and a wide range of concentrations of both components. Trends in interparticle spacings correlations as well as fractal dimensions of assemblies with varying PE and NP concentrations will be discussed, presenting a comprehensive narrative of the hierarchical structure of PE-NP self-assemblies. A general collapse of these trends on a master curve will be highlighted, providing universal guidelines for tailoring the microstructure of these assemblies. |
Tuesday, March 16, 2021 2:06PM - 2:18PM Live |
F02.00010: Random Copolymer Polyelectrolyte Complexes and the Role of Local Heterogeneity in Removing Organic Contaminants from Water Jeremy Wang, Curt Waltmann, Han Noe Umana Kossio, Monica Olvera De La Cruz, John Torkelson A polyelectrolyte complex consisting of an anionic polysoap with hydrophobic, hydrophilic and charged groups and a cationic copolymer with hydrophilic and charged groups is investigated for its ability to encapsulate organic molecules in aqueous solution. Cationic, anionic, and hydrophobic dyes were found to be effectively sequestered into the complex, and the macroscopic nature of the polyelectrolyte complex facilitates its easy removal from water. This highlights a potential application in removing a wide variety of organic contaminants from water with a single technique. Coarse-grained molecular dynamics simulations of the system reveal that hydrophobic interactions play a major role in complex formation and local heterogeneity in charge distribution arising from the random nature of the polyelectrolyte copolymers play a key role in the encapsulation of charged organic molecules. |
Tuesday, March 16, 2021 2:18PM - 2:30PM Live |
F02.00011: Loop-in coacervation in non-stoichiometric polyelectrolyte mixtures Sean Friedowitz, Junzhe Lou, Kayla Barker, Yan Xia, Jian Qin The response of coacervation window to salt addition in non-stoichiometric polyelectrolyte solutoins is examined by a joint experimental and theoretical effort. Polymer concentration in the coacervates is found to first increase with salt, then decrease, giving rise to a unique loop-in shape that is absent in symmetric mixtures. An asymptotic analysis in the low-salt regime shows that this loop-in behavior is caused by the osmotic pressure of the counterions confined in the coacervate due to electroneutrality, and that the effect is more prominent in solutions with stronger stoichiometric asymmetry. By labeling polycation and polyanion with distinct fluorescent labels, we resolved the partition coefficinets of polyions between the coexisting phases. The resutls showed that the polyions can only partially neutralize each other in the coacervates, and the excess are expelled to the supernatant. |
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