A coarse-grained thermodynamic model for the predictive engineering of valence-selective membranes

Rathee, Vikramjit S.; Qu, Siyi; Phillip, William A.; Whitmer, Jonathan K.

doi:10.1039/c6me00045b

Cited by 18 publications

(18 citation statements)

References 59 publications

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“…To validate the selectivity of PAP channels, we performed a series of steered MD simulations on two selected dye molecules 75 . We chose MO (328 Da) and RB (1018 Da), based on the selectivity experiments of PAP with MO able to transport through the channel and RB rejected.…”

Section: Methodsmentioning

confidence: 99%

Achieving high permeability and enhanced selectivity for Angstrom-scale separations using artificial water channel membranes

et al. 2018

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Synthetic polymer membranes, critical to diverse energy-efficient separations, are subject to permeability-selectivity trade-offs that decrease their overall efficacy. These trade-offs are due to structural variations (e.g., broad pore size distributions) in both nonporous membranes used for Angstrom-scale separations and porous membranes used for nano to micron-scale separations. Biological membranes utilize well-defined Angstrom-scale pores to provide exceptional transport properties and can be used as inspiration to overcome this trade-off. Here, we present a comprehensive demonstration of such a bioinspired approach based on pillar[5]arene artificial water channels, resulting in artificial water channel-based block copolymer membranes. These membranes have a sharp selectivity profile with a molecular weight cutoff of ~ 500 Da, a size range challenging to achieve with current membranes, while achieving a large improvement in permeability (~65 L m−2 h−1 bar−1 compared with 4–7 L m−2 h−1 bar−1) over similarly rated commercial membranes.

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Section: Methodsmentioning

confidence: 99%

Achieving high permeability and enhanced selectivity for Angstrom-scale separations using artificial water channel membranes

et al. 2018

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“…Polyelectrolytes are the basis for a broad class of functional systems including self-assembled copolymer membranes, polymer-coated nanoparticles, polyelectrolyte microgels, and hydrogel networks [1,2,3,4,5,6,7,8,9,10,11]. Though regarded as innately charged, polyelectrolytes frequently contain weakly acidic or basic moieties distributed along the polymer backbone.…”

Section: Introductionmentioning

confidence: 99%

Explicit Ion Effects on the Charge and Conformation of Weak Polyelectrolytes

et al. 2019

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The titration behavior of weak polyelectrolytes is of high importance, due to their uses in new technologies including nanofiltration and drug delivery applications. A comprehensive picture of polyelectrolyte titration under relevant conditions is currently lacking, due to the complexity of systems involved in the process. One must contend with the inherent structural and solvation properties of the polymer, the presence of counterions, and local chemical equilibria enforced by background salt concentration and solution acidity. Moreover, for these cases, the systems of interest have locally high concentrations of monomers, induced by polymer connectivity or confinement, and thus deviate from ideal titration behavior. This work furthers knowledge in this limit utilizing hybrid Monte Carlo–Molecular Dynamics simulations to investigate the influence of salt concentration, pK a , pH, and counterion valence in determining the coil-to-globule transition of poorly solvated weak polyelectrolytes. We characterize this transition at a range of experimentally relevant salt concentrations and explicitly examine the role multivalent salts play in determining polyelectrolyte ionization behavior and conformations. These simulations serve as an essential starting point in understanding the complexation between weak polyelectrolytes and ion rejection of self-assembled copolymer membranes.

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“…Moreover, the distance between the charged moiety and the pore wall (i.e., the spacer arm length) affected the free energy barrier for ion entry into the membrane. 137 A consistent increase in the size of the free energy barrier was observed with increasing spacer arm lengths because the longer chains pushed the terminal charges toward the center of the pore and increased their repulsive coverage (Fig. 7b).…”

Section: Modifying the Pore Wall Chemistry For Advanced Solute Separamentioning

confidence: 62%

Fit-for-purpose block polymer membranes molecularly engineered for water treatment

et al. 2018

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Continued stresses on fresh water supplies necessitate the utilization of non-traditional resources to meet the growing global water demand. Desalination and hybrid membrane processes are capable of treating non-traditional water sources to the levels demanded by users. Specifically, desalination can produce potable water from seawater, and hybrid processes have the potential to recover valuable resources from wastewater while producing water of a sufficient quality for target applications. Despite the demonstrated successes of these processes, state-of-the-art membranes suffer from limitations that hinder the widespread adoption of these water treatment technologies. In this review, we discuss nanoporous membranes derived from self-assembled block polymer precursors for the purposes of water treatment. Due to their well-defined nanostructures, myriad chemical functionalities, and the ability to molecularly-engineer these properties rationally, block polymer membranes have the potential to advance water treatment technologies. We focus on block polymer-based efforts to: (1) nanomanufacture large areas of highperformance membranes; (2) reduce the characteristic pore size and push membranes into the reverse osmosis regime; and (3) design and implement multifunctional pore wall chemistries that enable solute-specific separations based on steric, electrostatic, and chemical affinity interactions. The use of molecular dynamics simulations to guide block polymer membrane design is also discussed because its ability to systematically examine the available design space is critical for rapidly translating fundamental understanding to water treatment applications. Thus, we offer a full review regarding the computational and experimental approaches taken in this arena to date while also providing insights into the future outlook of this emerging technology.

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A coarse-grained thermodynamic model for the predictive engineering of valence-selective membranes

Abstract: We propose a minimal coarse-grained model capable of capturing the performance and guiding the design of copolymer membranes tailored for ion-separations.

Cited by 18 publications

References 59 publications

Achieving high permeability and enhanced selectivity for Angstrom-scale separations using artificial water channel membranes

Achieving high permeability and enhanced selectivity for Angstrom-scale separations using artificial water channel membranes

Explicit Ion Effects on the Charge and Conformation of Weak Polyelectrolytes

Fit-for-purpose block polymer membranes molecularly engineered for water treatment

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