Complex coacervation of statistical polyelectrolytes: role of monomer sequences and formation of inhomogeneous coacervates

Yu, Boyuan; Rumyantsev, Artem M.; Jackson, Nicholas E.; Liang, Heyi; Ting, Jeffrey; Meng, Siqi; Tirrell, Matthew; Pablo, Juan

doi:10.1039/d1me00076d

Cited by 15 publications

(23 citation statements)

References 83 publications

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“…Extensive studies have sought to understand how the equilibrium and rheological properties of complex coacervates can be altered by charge fraction, monomer sequence, added salt concentration, and so forth. − However, the majority of past work has focused on isotropic (and homogeneous rather than microphase separated − ) coacervate phases. When considering coacervation in the context of bioPEs, an important feature is that polyanions, particularly double-stranded DNA (dsDNA) and/or polycations, have limited flexibility.…”

Section: Introductionmentioning

confidence: 99%

Isotropic-to-Nematic Transition in Salt-Free Polyelectrolyte Coacervates from Coarse-Grained Simulations

Liang

Rumyantsev

et al. 2022

Macromolecules

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Recent interest in complex coacervation between oppositely charged polyelectrolytes (PEs) has been fueled by its relevance to biology in the context of membraneless organelle formation within living cells. For PEs with limited flexibility (such as double-stranded DNA), theoretical treatments and recent experiments have reported the emergence of liquid crystalline order (LCO) within the resulting coacervate phases. In this work, we study the underlying physics of this phenomenon using coarse-grained molecular dynamics simulations of symmetric semiflexible–semiflexible and asymmetric semiflexible–flexible coacervates. By comparing coacervates with the corresponding semidilute solutions of neutral polymers, we demonstrate that the presence of Coulomb interactions in coacervates facilitates orientational ordering, in agreement with theoretical predictions. Quantitative comparisons between our simulations and theory indicate that, for asymmetric nematic coacervates, the strong orientational ordering of stiff polyanions induces a weak ordering of the flexible polycationsan effect that was not anticipated by available theoretical studies. Simulations reveal that, for nematic coacervates, the preferred orientation of the PE chains at the liquid–liquid coacervate–supernatant interface is parallel, and the alignment of semiflexible PEs is homogeneous. The results presented here provide new molecular-level insights into the intra-coacervate LCO and will help motivate further experimental and theoretical activities in this area.

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Section: Introductionmentioning

confidence: 99%

Isotropic-to-Nematic Transition in Salt-Free Polyelectrolyte Coacervates from Coarse-Grained Simulations

Liang

Rumyantsev

et al. 2022

Macromolecules

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“…Over 50 years later, Spruijt and co-workers demonstrated experimentally the predictions of VO theory regarding the effects of salt concentration and polymer chain length on the phase coexistence . Experimental studies have since pushed the limits of VO theory by exploring the effects of hydrophobic interactions, pH, hydrogen bonding, − and variations in monomer sequence. − These studies have accordingly led to more sophisticated theories and simulations of complex coacervation, which have incorporated effects of charge regulation and ion-binding, ,− excluded volume, − dipole–dipole interactions, , charge connectivity and electrostatic correlations, ,− ,− and charge sequence. − ,− These advances have also been documented in recent reviews on polyelectrolyte solutions. ,− …”

Section: Introductionmentioning

confidence: 99%

Electrostatic Correlations and Temperature-Dependent Dielectric Constant Can Model LCST in Polyelectrolyte Complex Coacervation

et al. 2021

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The ability of polyelectrolytes to condense into a liquidlike, polyelectrolyte-rich phase out of a dilute supernatant phase through complex coacervation has led to fascinating phenomena, such as membraneless organelles and self-assembled capsules for drug delivery. Recent experiments have demonstrated that heating above a lower critical solution temperature (LCST) can drive complex coacervation. Here, we show that a coarsegrained model of electrostatic correlations is sufficient to model an LCST when accounting for the empirical decrease in the dielectric constant of the solvent upon heating. The predictions of the model agree qualitatively with experimental measurements of the compositions of the coexisting coacervate and supernatant phases. The model also achieves modest quantitative agreement with experiments, despite incorporating no other experimental parameters besides the dielectric constant and a fitted length scale. This agreement underscores the important role that can be played by electrostatic correlations in driving complex coacervation above an LCST.

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“…In that case, microphase separated structure may appear, in which dense domains of charged blocks coexist with the regions enriched with neutral blocks, as confirmed by theory 78 and simulation. 89 Besides, the charge association and dissociation may play extremely important roles in determining the properties of polyelectrolyte coacervation system, which is not included in the present study. In our model, we only consider weakly charged polyelectrolytes and assume that the charges of each chain remain fixed.…”

Section: ■ Conclusionmentioning

confidence: 99%

“…In this part, we set τ to be 3, 6, 15, 30, 75, and 150 for polycations A and B. For the polyelectrolytes with very long block length, they will likely undergo microphase separation and form micelles, 89 especially for diblock copolymers. 78 In the present work, we will focus on the polyelectrolytes being only capable of undergoing macrophase separation, which leads to the LLPS.…”

Section: ■ Introductionmentioning

confidence: 99%

Multiphase Coacervation of Polyelectrolytes Driven by Asymmetry of Charged Sequence

Chen

Yang

2022

Macromolecules

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The complex coacervation of oppositely charged polyelectrolytes is an important issue, which is relevant to many biological and industrial applications. While various biomolecules have been observed to form hierarchical multiphase structures in cells, its mechanism is still not fully understood. Here, we theoretically study the complex coacervation between the polyanion C and polycations A and B in solution and focus on the influence of charge sequence along the polyions on the multiphase coacervation. The electrostatic free energy is calculated with random phase approximation, and the phase diagrams are constructed by using the convex hull algorithm. It is revealed that the large asymmetry of charge patterns between A and B chains may induce the multiphase separation, driving the formation of two condensed phases, AC coacervate and BC coacervate, coexisting with a dilute phase. On the basis of our result, we propose a good criterion to determine if multiphase separation occurs or not. Furthermore, we analyze the effect of charge sequence of polyanion C as well as the addition of salt on the multiphase coacervation. This work provides insights into the underlying physics of sequence-dependent electrostatic interactions and the design of complex coacervates of polyelectrolyte mixtures.

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Complex coacervation of statistical polyelectrolytes: role of monomer sequences and formation of inhomogeneous coacervates

Abstract: Monomer sequences in statistical (co)polyelectrolytes can be used to tune complex coacervation, including density and structure of the polymer-rich phase.

Cited by 15 publications

References 83 publications

Isotropic-to-Nematic Transition in Salt-Free Polyelectrolyte Coacervates from Coarse-Grained Simulations

Isotropic-to-Nematic Transition in Salt-Free Polyelectrolyte Coacervates from Coarse-Grained Simulations

Electrostatic Correlations and Temperature-Dependent Dielectric Constant Can Model LCST in Polyelectrolyte Complex Coacervation

Multiphase Coacervation of Polyelectrolytes Driven by Asymmetry of Charged Sequence

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