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 B15: Polyelectrolyte Complexation |
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Sponsoring Units: DPOLY Chair: Scott Danielsen, Duke University Room: Room 207 |
Monday, March 6, 2023 11:30AM - 11:42AM |
B15.00001: Divalent cation-mediated polyanion attraction in an aqueous solution Alec Glisman, Sriteja Mantha, Zhen-Gang Wang, Decai Yu, Thomas Kalantar, Christopher Tucker, Eric Wasserman, Scott Backer, Larisa Reyes, Dipti Singh Polyelectrolytes are known to passivate/delay limescale (CaCO3) crystallization from aqueous suspension. Negatively charged functional groups along the polymer backbone chelate cations and form both intrachain and interchain ion bridges. At sufficiently high ionic strengths, these ion bridges lead to attractive interactions between the polyanions and precipitate polymer-ion complexes out of suspension. Polyelectrolyte effectiveness in preventing scale formation depends on its ability to chelate more Ca2+ ions before precipitation. The critical Ca2+ concentration is known as the Ca-tolerance of the polyelectrolyte. Our objective is to design polyelectrolytes with higher Ca-tolerance. We use the thermodynamic stability criterion and relate the Ca-tolerance of a polyelectrolyte to the potential of mean force (PMF) between two polyelectrolyte chains in an aqueous Ca2+ salt solution. We employ well-tempered metadynamics and Hamiltonian replica exchange protocols to calculate the two-chain PMF from molecular simulations. We systematically characterize the effect of solution ionic strength, temperature, functional groups, and molecular weight of the polyelectrolyte on the two-chain PMF. We will clarify the mechanism through which multi-valent ions result in the precipitation of the polyelectrolyte and present design principles for polyelectrolytes with higher Ca-tolerance values. |
Monday, March 6, 2023 11:42AM - 11:54AM |
B15.00002: Structure of polyelectrolyte and multi-valent ion complexes Alec Glisman, Sriteja Mantha, Zhen-Gang Wang, Decai Yu, Thomas Kalantar, Christopher Tucker, Eric Wasserman, Scott Backer, Larisa Reyes, Dipti Singh Experiments have established the ability of aqueous polyelectrolytes to passivate and delay the crystallization of limescale (CaCO3). Polyelectrolytes are expected to influence the CaCO3 crystallization by chelating Ca2+ ions from the solution and modifying the crystal growth by preferentially adsorbing to certain crystal surfaces. These processes may potentially delay the onset of nucleation and crystal growth, respectively. However, the mechanism through which polyelectrolytes operate is currently unknown. The binding of a Ca2+ to a charged residue on the polymer backbone is strongly dependent on the charge state of a polymer and its conformation, which are affected by the pH, concentration of Ca2+, and the overall ionic strength of the solution. The ability of a polyelectrolyte to sequester free Ca2+ depends on the polyelectrolyte-Ca2+ binding energy. We conduct molecular dynamics simulations with enhanced sampling techniques to study the interaction of Ca2+ with various polyanions in an aqueous suspension. We will present our findings on the polyelectrolyte-Ca2+ binding energetics, comment on the preferential Ca2+ binding sites on a polyelectrolyte backbone, and discuss their impact on the backbone conformations. |
Monday, March 6, 2023 11:54AM - 12:06PM |
B15.00003: The Interplay of Polymer Structure and Solvent Ordering on The Thermodynamics of Polyelectrolyte Solutions Michael Beckinghausen From adhesives to pharmaceuticals, complex coacervation appears in many industrial applications and consumer products, motivating growing interest in the underlying thermodynamics and morphology. However, a significant challenge remains in building a reliable theoretical formulation that captures long-range electrostatic correlations and properly relates nanoscale structure and fluctuations to collective thermodynamic behavior. We study the effect of dipole ordering on the electrostatic potential near a charged surface and the phase behavior of oppositely charged polymer solutions. Our theoretical model of a solution of polyelectrolytes within a polar solvent aims to accurately capture polymer structure and solvent ordering at the nanoscale. We leverage exact results for the statistical behavior of the wormlike chain model in tandem with the random phase approximation. We show that the choice of chain structure factors predicts a wide range of phase behavior over a range of polymer lengths when accounting for quadratic order fluctuation corrections. We also demonstrate that our explicit treatment of the polar solvent leads to more significant charge-charge interactions near the polymers. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B15.00004: The Effect of Cation-π Interactions on the Relaxation Dynamics of Polyelectrolyte Complex Coacervates Conner H Chee We investigate the effect of cation-π interactions in determining the relaxation dynamics of polyelectrolyte complex (PEC) coacervates by studying their rheology in the presence of salts with different cation-π interaction strengths. We prepare a bulk, salt-free PEC composed of poly(styrene 4-sufonate) (PSS) and poly(diallyldimethylammonium) (PDADMA) and use a salt addition method to prepare coacervate samples with identical salt and polymer concentrations but differing inorganic salts. We find that the viscosity and relaxation times of the coacervates increase as the cation is changed from K+, to Na+ to Li+. This trend is consistent with the known cation-π interaction strengths of the three cations, with K+ engaging in the strongest binding with aromatic rings on the PSS and thus the most effectively out-competing stabilizing cation-π interactions between the chains. These findings show that cation-π interactions can play an important role in determining the dynamics of PECs and should be accounted for when interpreting rheological data on these materials. |
Monday, March 6, 2023 12:18PM - 12:30PM |
B15.00005: Upper critical solution temperature behavior of a strong-weak polyelectrolyte complex in acid medium Chikaodinaka I Eneh Phase separation is entropically favored when oppositely charged polyelectrolytes are mixed, releasing small counterions to form intrinsic ion pairs. This results in the formation of a supernatant phase and a dense, solid or liquid coacervate phase containing polyelectrolyte complexes (PECs). Understanding PECs is valuable for advancing drug delivery systems, underwater adhesives, and multi-compartment cells. PEC phase boundaries have most commonly been explored with respect to salt and polymer concentration, pH, and mixing ratio. More recently, the effects of temperature on the phase transitions of PECs have gained interest but a gap in knowledge still remains. In this study, using turbidity and conductivity measurements, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and optical microscopy (OM), we identify the phase boundaries of poly(diallyldimethyl ammonium)/poly(acrylic acid) (PDADMA/PAA) PECs at pH 3. We observe reversible temperature-induced phase transitions showing upper critical solution temperature (UCST) behavior at different PDADMA:PAA mixing ratios and ionic strengths. These results provide more understanding of salt, water, and temperature contributions to phase transitions. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B15.00006: Scattering Evidence of Charge Correlations in Polyelectrolyte Coacervates Yan Fang, Angelika S Neitzel, Heyi Liang, Artem Rumyantsev, Yuanchi Ma, William T Heller, Juan J De Pablo, Matthew V Tirrell Polyelectrolyte complex coacervation plays a crucial role in biological processes. Rational design of coacervate-based materials/assemblies requires understanding the internal structure of the complexes. Despite broad consensus among different theoretical methods, the existence of positional charge correlations in complex coacervates remains a hypothesis that has not been confirmed experimentally. Small angle scattering (SAS) experiments with X-rays (SAXS) or neutrons (SANS) are employed to study the internal structure of polyelectrolyte complex coacervates. Past SAS profiles have confirmed the structural similarity of polyelectrolyte complex coacervates to semidilute solutions of neutral polymers where the resultant total scattering function exhibits an Ornstein-Zernike (OZ) form. However, these studies have not provided insight into positional correlations of charges within the complexes. To access charge correlations, scattering from either the polyanions or polycations exclusively is required. We have achieved this through deuterium labeling of one type of polyelectrolyte and solvent contrast matching. The scattering function of polyanions exhibits the scattering peak at the correlation length scale, which gradually disappears and reconstitutes OZ form at high salt concentrations. Experimental scattering results are consistent with the RPA-based theoretical analysis and coarse-grained molecular dynamics simulations. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B15.00007: Polyelectrolyte and anti-polyelectrolyte effects on chain conformations of polyzwitterions Rajeev Kumar, Zening Liu, Yangyang Wang, Jong K Keum, Kunlun Hong, Bobby G Sumpter Polyzwitterions are considered as model synthetic analogues of intrinsically disordered proteins. Based on this analogy, polyzwitterion chains in dilute aqueous solutions |
Monday, March 6, 2023 12:54PM - 1:06PM |
B15.00008: Asymmetry in charge density and size in polymer complexation: partially ionizable polyelectrolytes and intrinsically disordered proteins Arindam Kundagrami, Soumik Mitra, Souradeep Ghosh, Aritra Chowdhury, Ben Schuler
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Monday, March 6, 2023 1:06PM - 1:18PM |
B15.00009: Effect of salt on diffusion of polyelectrolyte in polyelectrolyte coacervates Suvesh M lalwani, Jodie Lutkenhaus
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Monday, March 6, 2023 1:18PM - 1:30PM |
B15.00010: Observing Departures from Expected Diffusion Behavior in Concentrated Polyelectrolyte Solutions Using Single Particle Tracking Harrison Landfield, Nicholas Kalamaris, Muzhou Wang Polyelectrolytes are of wide experimental interest due to their biological origins and the unique applications rooted in leveraging their charge-carrying groups. Effective design of polyelectrolyte systems for industrial uses requires understanding of how these polymers interact with neighboring chains. Polyelectrolyte diffusion is central to the success of these applications, often deviates from neutral polymer behavior, and allows us to gauge solution self-assembly. We used single particle tracking (SPT) to study the effect of ion and polymer concentration on the diffusion behavior of polyelectrolyte solutions to measure the relative effects of physical and charge-based interactions using polylysine (PL). These solutions show that PL diffuses as a single, Fickian population that has a strikingly strong concentration dependence on diffusivity. This is indicative of high degrees of interaction and ordering between neighboring chains. Changes in counterion concentrations and valency lead to large differences in the resulting MSD values of the polymers but the strong concentration dependence on diffusivity is retained. This work is further supplemented by complementary techniques to provide a molecular explanation of interpolymer interactions and measure diffusivity over a broad concentration range. Notably, the strong concentration dependence occurs in a concentration regime that is obtainable using fluorescence-based SPT but unanalyzable using other common experimental methods. |
Monday, March 6, 2023 1:30PM - 1:42PM |
B15.00011: Identifying the Glass Transitions and Material Properties of Polyelectrolyte Complex Materials Sarah L Perry, Isaac A Ramírez Marrero, Rainer Gutzler, Nadine Kaiser, Bernhard von Vacano, Rupert Konradi The formulation of functional polymeric materials, like adhesives and coatings, is particularly challenging due to the interplay between performance and processability, such as the use of organic solvents, which can be detrimental to the environment. Complex coacervation is an entropically driven, associative, aqueous liquid-liquid phase separation that results in a polymer-rich coacervate, and a polymer-poor supernatant. We propose using coacervation as an alternative, environmentally friendly, processing strategy for producing solid films of polyelectrolyte complexes by removal of salt. However, it is unclear whether the design rules associated with traditional polymers will hold for PEC materials. To understand the design space, we developed a library of methacrylate copolymer PECs of varying charge and hydrophobicity, which we have characterized using dynamic mechanical analysis and tensile tests. Our data show that varying charge and hydrophobicity allows for a wide range of mechanical behavior, ranging from brittle to ductile. We also highlight the effect of temperature, humidity, and salt on the glass transitions of these materials to show how we can use these parameters in processing and to achieve different mechanical responses. The responsiveness of PEC materials could be harnessed for a variety of applications, including adhesives and coatings. As such, PECs hold promise as robust materials that provide enhanced performance in tandem with a lower environmental footprint. |
Monday, March 6, 2023 1:42PM - 1:54PM |
B15.00012: Local Correlations and Molecular Origin of Parameters in the Transfer Matrix Theory of Coacervation Charles E Sing Polymeric complex coacervation is an associative phase separation process that is driven by the electrostatic attraction between oppositely-charged polyelectrolytes in solution. This phase separation results in a polymer-dense ‘coacervate’ phase and a polymer-dilute ‘supernatant’ phase, with the coacervate phase in particular finding widespread use in industrial applications (such as food and personal care products) and as a model system for biomolecular condensates. There has been significant effort in the polymer physics community to study these materials, using a wide variety of theoretical approaches to understand the underlying physics of this phase separation phenomenon. One approach, the transfer matrix theory, maps the problem of coacervation to a one-dimensional adsorption model to keep track of its interactions with surrounding particles. This model has been successful at making predictions of coacervate phase behavior, and how it is affected by several molecular effects such as polyelectrolyte stiffness, monomer sequence, multivalent salts, pH, and polymer architecture. However, the transfer matrix model relies on several empirical fit parameters whose connection to molecular structure has been unclear. We can now show, using cluster expansions, how to derive expressions for these parameters that relate to underlying polymer connectivity and interactions. These parameters give reasonable predictions for phase behavior consistent with known phase behavior in polyelectrolyte coacervates, and provide the foundation for more rigorously explaining molecular effects on coacervation. |
Monday, March 6, 2023 1:54PM - 2:06PM |
B15.00013: Impact of Bottlebrush Polyelectrolytes on Polyelectrolyte Complex Physical Properties Kaden C Stevens, Matthew V Tirrell
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Monday, March 6, 2023 2:06PM - 2:18PM |
B15.00014: Various Types of Polyampholyte Necklaces: Charge-in-Beads, Charge-in-Strings, and Hierarchical Structures Yiheng Wu, Artem Rumyantsev, Juan J De Pablo Polyampholytes are considered synthetic analogs of intrinsically disordered proteins (IDPs). In our previous work [1], we provided scaling predictions for single-chain conformations of charge-imbalanced Markov polyampholytes in theta solvent. Two distinct types of polyampholyte necklaces were predicted: charge-in-beads and charge-in-strings necklaces. |
Monday, March 6, 2023 2:18PM - 2:30PM |
B15.00015: Coacervate Formation in Dilute Aqueous Solution of 2.5-nm Size Molecular Macroanions with Simple Di- or Trivalent Cations Kexing Xiao, Yuqing Yang, Xiaohan Xu, Yifan Zhou, Jennifer Szymanowski, Ginger E Sigmon, Peter C Burns, Tianbo Liu Complex coacervates are commonly thought to be formed from the liquid-liquid phase separation of two oppositely charged polyelectrolytes in aqueous solutions, due to mainly the electrostatic attraction followed by entropy-driven release of small counterions near the polyelectrolytes. Here, we report a completely unique coacervate formed by a water soluble uranyl peroxide molecular cluster (Li68K12(OH)20)[UO2(O2)-OH]60, U60) in the presence of only di- or trivalent countercations. Three distinct phases: homogenous solution, biphasic coacervate and gel, are observed in dilute aqueous solution with varied salt-to-U60 molar ratios. To the best of our knowledge, this is the first example of coacervation between only macroion clusters and small simple counterions without any large-sized polyelectrolytes involved. The formation of the coacervate by the U60/di/trivalent cations is confirmed by combined techniques, including turbidity, rheology and transmission electron microscopy (TEM). Unlike the conventional polyelectrolyte complexation, the U60 coacervate complexes can be formed over a much broader range of salt-to-U60 molar ratio. The dependence of coacervate formation on the salt-to-U60 molar ratio is attributed to the balance of the non-covalent interactions. Moreover, TEM characterization reveals large, thin-film-like nanosheet structures of the coacervates. The imbalance between macroions and small multivalent counterions leads to counterion association around U6060- macroions and consequently the counterion-mediated attraction among macroions, resulting in their assembly into 2-D nanosheet structures. In the presence of stronger di-or trivalent counterions, the rigid nanosheets do not close to form well-studied hollow, spherical, single-layered blackberry structures, by stay open and stack closely forming gel and coacervates in dilute aqueous solutions. |
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