Polyelectrolyte Brush Layer Research Articles

All-atom molecular dynamics simulations showing the dynamics of small organic molecules in water-solvated polyelectrolyte brush layers.

Polyelectrolyte brushes can introduce functionality to surfaces and because of this, these brushes have been studied extensively. In many applications, these brushes are used in solutions that contain a variety of molecules. While the interaction between polyelectrolyte brushes and molecules has been studied via coarse-grained simulations and experiments, such interaction has not been studied in molecular detail. An understanding of interactions in such molecular detail may prove crucial in the design of future brush coatings that can enable desired adsorption of different organic and biological molecules. Therefore, we present a first all-atom molecular dynamics simulations study of poly(sodium acrylate) brushes in contact with a small organic molecule, γ-butyrolactone. Within this molecular framework, we study the interaction of this lactone molecule with the brush layer and study the ensuing absorption and dynamics of the lactone inside the brush layer. The lactone is found to prefer to remain in the bulk solution; however, when absorbed, lactone molecules are found to have significantly reduced mobilities as compared to that in the bulk solution and are able to massively influence the properties of the brush-entrapped water molecules. These findings provide unprecedented details about the absorption-driven changes to molecular structure and dynamics of the lactone molecules and the water molecules inside the brush layer and can only be uncovered by our all-atom MD simulations. Such explicit and atomistically-resolved information, taking into account the specific chemical nature of the interacting systems, is rare in the context of designing polymer and PE brush-based coatings. Thus, we anticipate that our findings will be crucial in the design of future brush coatings aimed at providing adsorption platforms for different organic and biomolecules.

Gated nanoparticle transport in a functional group modified nanopore

Inspired by nature, functionalized nanopores have become an important platform in the field of sensing. In this article, we constructed a mathematical model for the gate-controlled manipulation of nanoparticle motion inside pH-responsive polyelectrolyte-modified nanopores and theoretically studied the synergistic control of gate electrode and polyelectrolyte brush layer on nanoparticle motion. By efficiently modifying the charge density and polarity of the polyelectrolyte brush layer located within the nanopore, the gate electrode is capable of actively regulating the velocity of nanoparticle transport through the nanopore. At a solution pH of 5, the higher the gate potential, the faster the nanoparticle transport through the nanopore, which is significantly different from the solution pH of 6. When the gate potential is negative, the degree of ion current blockage increases with increasing gate potential. These results establish a theoretical foundation for the development of novel functionalized nanopores that can be utilized in the field of nanopore sensing.

Specific Ion and Electric Field Controlled Diverse Ion Distribution and Electroosmotic Transport in a Polyelectrolyte Brush Grafted Nanochannel.

Controlling ion distribution inside a charged nanochannel is central to using such channels in diverse applications. Here, we show the possibility of using a charged polyelectrolyte (PE) brush-grafted nanochannel for triggering diverse nanoscopic ion distribution and nanofluidic electroosmotic transport by controlling the valence and size of the counterions (that screen the charges of the PE brushes) and the strength of an externally applied axial electric field. We atomistically simulate separate cases of fully charged polyacrylic acid (PAA) brush functionalized nanochannels with Na+, Cs+, Ca2+, Ba2+, and Y3+ counterions screening the PE charges. Four key findings emerge from our simulations. First, we find that the counterions with a greater valence and a smaller size prefer to remain localized inside the brush layer. Second, for the case where there is an added chloride salt with the same cation (as the screening counterions), there are more coions (Cl- ions) in the brush-free bulk than counterions (for counterions Na+, Ca2+, Ba2+, Y3+): this is a manifestation of the overscreening (OS) of the PE brush layer. Contrastingly, the number of Cs+ ions remain higher than the Cl- ions inside the brush-free bulk, ensuring that there is no OS effect for this case. Third, large applied electric field enables a few Na+, Cs+, and Ba2+ counterions to leave the brush layer and to go to the bulk: this makes the OS of the PE brush layer disappear for the cases of PE brushes being screened by the Na+ and Ba2+ ions. On the other hand, no such electric-field-mediated disappearance of OS is observed for the cases of Ca2+ and Y3+ screening counterions; we attribute this to the firm attachment of these counterions to the negatively charged monomers. Free energy associated with a counterion binding to a PE chain corroborates this diversity in the counterion-specific response to the applied electric field. Finally, we demonstrate that such diverse ion distributions, along with specific electric-field-strength-dependent ion properties, lead to (1) electroosmotic (EOS) transport in nanochannels grafted with PAA brushes screened with Cs+ ions to be always counterion dominated, (2) EOS transport in nanochannels grafted with PAA brushes screened with Ca2+ and Y3+ ions to be always coion-dominated, and (3) EOS transport in nanochannels grafted with PAA brushes screened with Na+ and Ba2+ ions to be coion dominated for smaller electric fields and counterion dominated for larger electric fields.

Electrokinetic transport of nanoparticles in functional group modified nanopores

Nanopore detection is a hot issue in current research. One of the challenges is how to slow down the transport velocity of nanoparticles in nanopores. In this paper, we propose a functional group modified nanopore. That means a polyelectrolyte brush layer is grafted on the surface of the nanopore to change the surface charge properties. The existing studies generally set the charge density of the brush layer to a fixed value. On the contrary, in this paper, we consider an essential property of the brush layer: the volume charge density is adjustable with pH. Thus, the charge property of the brush layer will change with the local H+ concentration. Based on this, we established a mathematical model to study the transport of nanoparticles in polyelectrolyte brush layer modified nanopores. We found that pH can effectively adjust the charge density and even the polarity of the brush layer. A larger pH can reduce the transport velocity of nanoparticles and improve the blockade degree of ion current. The grafting density does not change the polarity of the brush charge. The larger the grafting density, the greater the charge density of the brush layer, and the blockade degree of ion current is also more obvious. The polyelectrolyte brush layer modified nanopores in this paper can effectively reduce the nanoparticle transport velocity and retain the essential ion current characteristics, such as ion current blockade and enhancement.

The interaction between silica flat substrate and functional group-modified nanoparticles.

Inspired by nature, the research of functionalized nanoparticles and nanodevices has been in-depth developed in recent years. In this paper, we theoretically studied the interaction between functional polyelectrolyte brush layer-modified nanoparticles and a silica flat substrate. Based on the Poisson-Nernst-Planck equations, the mathematical model is established. The changes of the volume charge density and electric field energy density when the nanoparticle interacts with the silica flat substrate under multi-ions regulation were investigated. The results show that when there is a strong interaction between the silica flat substrate and nanoparticles, such as the distances between the nanoparticle and silica flat substrate, which are 2 or 5nm, the isoelectric point shift under the influence of silica flat substrate and the total charge density in the brush layer is jointly controlled by the cations in the solution and the volume charge density of the brush layer. With the increase of the distances between the nanoparticle and silica flat substrate, the regulation of the volume charge density of the brush layer dominates. These results will provide guidance for the movement mechanism of functionalized nanoparticles in silica nanochannels.

Bioinspired Design of a Cartilage-like Lubricated Composite with Mechanical Robustness.

Natural articular cartilages show extraordinary tribological performance based on their penetrated surface lubricated biomacromolecules and good mechanical tolerance. Hydrogels are considered to be potential alternatives to cartilages due to their low surface friction and good biocompatibility, although the poor mechanical properties limited their applications. Inspired by the excellent mechanical properties and the remarkable surface lubrication mechanism of natural articular cartilages, one kind of cartilage-like composite material with a lubrication phase (Composite-LP) was developed by chemically grafting a thick hydrophilic polyelectrolyte brush layer onto the subsurface of a three-dimensional manufactured elastomer scaffold-hydrogel composite architecture. The Composite-LP exhibited good load-bearing capacities because of the nondissipation strategy and the stress dispersion mechanism resulting from the elastomer scaffold enhancement. In the presence of the top lubrication layer, the Composite-LP showed superior friction reduction functionality and wear resistance under a dynamic shearing process. This design concept of coupling the non-dissipative mechanism and interface lubrication provides a new avenue for developing cartilage-like hydrogels and soft robots.

Machine learning enabled quantification of the hydrogen bonds inside the polyelectrolyte brush layer probed using all-atom molecular dynamics simulations.

The configuration of densely grafted charged polyelectrolyte (PE) brushes is strongly dictated by the properties and behavior of the counterions that screen the PE brush charges and the solvent molecules (typically water) that solvate the brush molecules and these screening counterions. Only recently, efforts have been made to study the PE brushes atomistically, thereby shedding light on the properties of brush-supported ions and water molecules. However, even for such efforts, there are limitations associated with using a generic definition to estimate certain properties of water and ions inside the brush layer. For example, water-water hydrogen bonds (HBs) will behave differently for locations outside and inside the brush layer, given the fact that the densely closely grafted PE brush molecules create a soft nanoconfinement where the water connectivity becomes highly disrupted: therefore, using the same definition to quantify the HBs inside and outside the brush layer will be unwise. In this paper, we address this limitation by employing an unsupervised machine learning (ML) approach to predict the water-water hydrogen bonding inside a cationic PE brush layer modeled using all-atom molecular dynamics (MD) simulations. The ML method, which relies on a clustering approach and uses the equilibrium coordinates of the water molecules (obtained from the all-atom MD simulations) as the input, is capable of identifying the structural modification of water-water HBs (revealed through appropriate clustering of the data) inside the PE brush layer induced soft nanoconfinement. Such capabilities would not have been possible by using a generic definition of the HBs. Our calculations lead to four key findings: (1) the clusters formed inside and outside the brush layer are structurally similar; (2) the margin of the cluster is shorter inside the PE brush layer confirming the possible disruption of the HBs inside the PE brush layer; (3) the average "hydrogen-acceptor-oxygen-donor-oxygen" angle that defines the HB is reduced for the HBs formed inside the brush layer; (4) the use of the generic definition (definition usable for characterizing the HBs in brush-free bulk) leads to an overprediction of the number of HBs formed inside the PE brush layer.

Enhanced Surface Icephobicity on an Elastic Substrate.

Ice accumulation on exposed surfaces is unavoidable as time elapses and the temperature decreases sufficiently. To mitigate icing problems, various types of icephobic substrates have been rationally designed, including superhydrophobic substrates (SHSs), aqueous lubricating layers, organic lubricating layers, organogels, polyelectrolyte brush layers, electrolyte-based hydrogels, elastic substrates, and multicrack initiator-promoted surfaces. Among these surfaces, elastic substrates show excellent enhanced surface icephobicity during dynamic processes (i.e., water-impacting and de-icing tests). Herein, we summarize recent progress in elastic icephobic substrates and discuss the reasons that surface icephobicity can be enhanced on elastic substrates in terms of enhanced water repellency and further lowering the ice adhesion strength. For enhanced water repellency, we focus on reducing the contact time of water impacting such that water droplets can be easily shed from an elastic substrate before ice occurs. Reducing the contact time of water impacting various substrates (i.e., micro/nanostructured rigid SHSs, macrotextured rigid SHSs, and elastic SHSs) is discussed, followed by exploring their mechanisms. We argue that the ice adhesion strength can be further lowered on an elastic substrate by rationally tuning the elastic modulus and surface textures (i.e., surface textured and hollow subsurface textured) and combining elastic substrate with other passive anti-icing strategies (or functioning passive icephobic substrates with an electrothermal or photothermal stimulus). In short, the introduction of an elastic substrate into a passive or active icephobicity surface opens an avenue toward designing a versatile icephobic surface, providing great potential for outdoor anti-icing applications.

Simultaneous Energy Generation and Flow Enhancement (Electroslippage Effect) in Polyelectrolyte Brush Functionalized Nanochannels.

Energy generation through nanofluidics is a topic of great nanotechnological relevance. Here, we conduct all-atom molecular dynamics (MD) simulations of the transport of water and ions in a pressure-driven flow in nanochannels grafted with charged polyelectrolyte (PE) brushes and discover the possibility of simultaneous electrokinetic energy generation and flow enhancement (henceforth denoted as the electroslippage effect). Such PE-brush-functionalized nanochannels have been recently shown to demonstrate an overscreening (OS) effect (characterized by the presence of a greater number of screening counterions within the PE brush layer than needed to screen the PE brush charges), a consequent presence of excess co-ions within the PE brush-free bulk, and a co-ion-driven electroosmotic (EOS) transport in the presence of small to moderate applied axial electric fields. In this study, however, we find that the streaming current, which represents the current generated by the flow-driven downstream advection of the charge imbalance present within the electric double layer (EDL) that screens the PE brush charges, is governed by the migration of the counterions. This stems from the fact that the highest contribution to the overall streaming current arises from the region near the PE brush-water interface (where there is an excess of counterions), while the brush-free bulk yields a hitherto unreported, but small, co-ion-dictated streaming current. This downstream advection of the charge imbalance (and the resultant counterion-driven streaming current) eventually leads to the development of an electric field (streaming electric field) in the direction that is opposite the direction of the counterion-driven streaming current. The streaming current and the streaming electric field interact to generate the electrokinetic energy. Equally important, this streaming electric field induces an EOS transport, which becomes co-ion-driven, due to the presence of excess co-ions in the brush-free bulk. For the case of nanochannels grafted with negatively charged PE brushes, the streaming electric field will be in a direction that is opposite that of the pressure-driven transport, and hence the co-ion (or anion) driven EOS flow will be in the same direction as the pressure-driven transport. On the other hand, for the case of nanochannels grafted with positively charged PE brushes, the streaming electric field will be in the same direction as the pressure-driven flow, and hence the co-ion (or cation) driven EOS flow, will again be in the same direction as the pressure-driven flow. Therefore, whenever there occurs a presence of the OS and the resulting co-ion-driven EOS transport in PE brush grafted nanochannels, regardless of the sign of the charges of the PE brushes, this EOS transport will always aid the pressure-driven transport and will cause the most fascinating increase in the net volume flow rate across the nanochannel cross section, which is the electroslippage effect.

Ultrafast Water Transport in Two‐Dimensional Channels Enabled by Spherical Polyelectrolyte Brushes with Controllable Flexibility

AbstractFast water transport channels are crucial for water‐related membrane separation processes. However, overcoming the trade‐off between flux and selectivity is still a major challenge. To address this, we constructed spherical polyelectrolyte brush (SPB) structures with a highly hydrophilic polyelectrolyte brush layer, and introduced them into GO laminates, which increased both the flux and the separation factor. At 70 °C, the flux reached 5.23 kg m−2 h−1, and the separation factor of butanol/water increased to ≈8000, which places it among the most selective separation membranes reported to date. Interestingly, further studies demonstrated that the enhancement of water transport was not only dependent on the hydrophilicity of the polyelectrolyte chains, but also influenced by their flexibility in the solvent. Quartz crystal microbalance with dissipation and molecular dynamics simulations revealed the structure‐performance correlations between water molecule migration and the flexibility of the ordered polymer chains in the 2D confined space.

Charge Properties and Electric Field Energy Density of Functional Group-Modified Nanoparticle Interacting with a Flat Substrate.

Functionalized nanofluidics devices have recently emerged as a powerful platform for applications of energy conversion. Inspired by biological cells, we theoretically studied the effect of the interaction between the nanoparticle and the plate which formed the brush layer modified by functional zwitterionic polyelectrolyte (PE) on the bulk charge density of the nanoparticle brush layer, and the charge/discharge effect when the distance between the particle and the plate was changed. In this paper, The Poisson–Nernst–Planck equation system is used to build the theoretical model to study the interaction between the nanoparticle and the plate modified by the PE brush layer, considering brush layer charge regulation in the presence of multiple ionic species. The results show that the bulk charge density of the brush layer decreases with the decrease of the distance between the nanoparticle and the flat substrate when the interaction occurs between the nanoparticle and the plate. When the distance between the particle and the plate is about 2 nm, the charge density of the brush layer at the bottom of the particle is about 69% of that at the top, and the electric field energy density reaches the maximum value when the concentration of the background salt solution is 10 mm.

Electrokinetics of non-Newtonian fluids in poly-electrolyte grafted nanochannels: Effects of ion-partitioning and confinement

Fluid flow inside nano-channels coated with a polyelectrolyte brush layer (PEL) is dictated by the brush structure and its interaction with the counter-ion dominated electrical double layer (EDL) near the walls of the PEL channel. In this work, we bring out the confluence of spatial permittivity variation, the influence of proximity between ions in charged PEL channels and non-Newtonian constitutive behavior of the fluid towards altering the electrokinetics of power-law fluids as well as their mechanical to electrical energy conversion capabilities. Our estimates are based on considering the fluidic drag experienced by the ions mediated by effective confinement induced by other ions and fluid rheology. For small electrical double layer (EDL) thicknesses (corresponding to high ionic concentrations), the energy conversion efficiency is shown to be higher for shear-thinning fluids, with a crossover in these characteristics for higher EDL thicknesses. Results show that lower bulk to PEL charge density ratio corresponds to higher conversion efficiencies. PEL also dictates ionic drag in that higher PEL thickness corresponds to higher ionic drag. It has been observed that although the electrokinetic parameters such as streaming potential (electrical potential generated across a channel due to a pressure-driven flow) and energy conversion efficiency (based on the ratio of electrical energy harvested to mechanical energy input) are significantly influenced by the fluid and the nanochannel properties, there exists a cross-over EDL thickness for the variation in the conversion efficiency, which is solely dependent on the properties of the nanochannel. The consideration of the ionic confinement effect allows us to have a more realistic estimate of energy conversion efficiency and yields better estimates of critical regimes of operation depending on EDL thickness for optimal efficiency. These results may yield insight towards designing functional nanofluidic devices with biological interfaces.

Preparation of Polyelectrolyte Brush Layer Modified Magnetic Particles for Separation of Proteins

Magnetic particles are a promising tool for separation of substantial proteins by applying an external magnetic field to collect the particles after adsorption of proteins. To provide much functionality on the magnetic particles for protein separation under mild condition and by easy procedures, polyelectrolyte brush layer was constructed on the surface. Magnetic polystyrene particles were prepared by mini-emulsion polymerization. Then the particles were modified with hydrophilic polyelectrolyte brush layer with different electric charges via atom transfer radical polymerization (ATRP). The polyelectrolyte brush layer could play an important role to endow the particles with good dispersion ability and also, control protein adsorption by electrostatic interaction. That is, the proteins having electric charges under biological environment could be adsorbed onto the magnetic particles with opposite-charged polymer brush layer and quickly collected from the solution. Thus we conclude that the magnetic particles with a polymer brush layer provide excellent functions.

Rectification of ionic current in nanopores functionalized with bipolar polyelectrolyte brushes

Abstract In this study, control of ion transport is demonstrated by surface modification of bipolar polyelectrolyte (PE) brushes on a nanopore wall. Three types of nanopore are considered: (i) Only the inner wall of a nanopore is modified and its outer walls are charge-free (type I). (ii) Only the outer walls of a nanopore are modified (type II) and its inner wall is charge-free. (iii) Both the inner and the outer walls of a nanopore are modified (type III). Results reveal that for the levels of salt concentration considered all these three types of nanopore show apparent current rectification. The rectification ability depends highly on both the structure and the space charge densities of the bipolar PE brush layers. For example, if the charge densities of this layer are low, the rectification ability of the types of nanopore ranks as type III > type II > type I; otherwise, it ranks as type III > type I > type II if they are sufficiently high. In addition, if the charge densities of those layers are symmetric, the rectification ability increases with increasing charge density for all three types of nanopore. For nanopores having asymmetric charge densities in their PE brush layers, similar charge density-dependent rectification behavior occurs only to type II nanopore. It is interesting to observe in the other two types of nanopore, the increase in the charge densities results in a decrease in the rectification effect. This is unexpected because previous studies suggested that the nanopore rectification depends positively on its charge density.

Heterogeneous Morphology and Dynamics of Polyelectrolyte Brush Condensates in Trivalent Counterion Solution

Recent experiments have shown that trivalent ion, spermidine$^{3+}$, can provoke lateral microphase segregation in DNA brushes. Using molecular simulations and simple theoretical arguments, we explore the effects of trivalent counterions on polyelectrolyte brushes. At a proper range of grafting density, polymer size, and ion concentration, the brush polymers collapse heterogeneously into octopus-like surface micelles. Remarkably, the heterogeneity in brush morphology is maximized and the relaxation dynamics of chain and condensed ion are the slowest at the 1:3 stoichiometric concentration of trivalent ions to polyelectrolyte charge. A further increase of trivalent ion concentration conducive to a charge inversion elicits modest reswelling and homogenizes the morphology of brush condensate. Our study provides a new insight into the origin of the diversity in DNA organization in cell nuclei as well as the ion-dependent morphological variation in polyelectrolyte brush layer of biological membranes.

Interaction between two parallel plates covered with a polyelectrolyte brush layer in an electrolyte solution

An approximate analytic expression is derived for the interaction energy between two parallel plates covered with a polyelectrolyte brush layer in an electrolyte solution. The interaction energy has three components: electrostatic interaction energy between two brush layers before and after their contact, steric interaction energy between two brush layers after their contact, and the van der Waals interaction energy between the cores of the plates. It is shown that these three components are of the same order of magnitude and contribute equally to the total interaction energy between two polyelectrolyte-coated plates in an electrolyte solution. On the basis of Derjaguin’s approximation, an approximate expression for the interaction energy between two spherical particles covered with polyelectrolyte brush layers is also derived.

Conductance Modulation in Silicon-on-Insulator Solid-State Nanopores Coated with Electroactive Polymers

Solid-state nanopores are an ideal platform for bioanalytical studies. However, only very few solid-state nanopores allow the ionic conductance through the nanopore to be modulated, which is a feature of most transmembrane protein channels. Using silicon-on-insulator (SOI) substrates, a substrate bias can be applied to the top silicon layer in which cylindrical nanopores have been formed, leading to a modulation of the ionic conductance through the nanopore.The effect of the electrostatic modulation on the nanopore conductance, however, is small unless the electrolyte concentration is low (<100 μM) or the pore diameter is below 10 nm. To increase the effect of the conductance modulation, polyelectrolyte brushes tethered to the inside of the nanopore can be used, which actively change the diameter of the lumen of the nanopore. Since the polymer brushes are charged, a change in surface charge due to an electrostatic bias is expected to influence the length of the brushes extending into the nanopore, thereby changing its diameter.In our experiments, poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA) polyelectrolyte brushes were deposited on the inner walls of thermally oxidized SOI cylindrical nanopores using surface-initiated atom transfer radical polymerization (SI-ATRP). After polymerization, the ionic conductance of the nanopore was characterized using DC conductance and Electrochemical Impedance Spectroscopy (EIS). The EIS data allowed a separation of the influence of the polyelectrolyte brushes on the nanopore conductance from the influence on the capacitance of the complete device, enabling the development of an equivalent electrical circuit model. Ion transport studies under both pH and gate bias stimuli revealed a significant conductance increase in strong acidic solutions (100 mM HCl) and a conductance modulation upon application of a positive gate bias in 100 μM HCl solutions, which was not observable without the polyelectrolyte brush layer.

Gated ion transport in a soft nanochannel with biomimetic polyelectrolyte brush layers

Functionalized nanofluidics has recently emerged as a powerful platform for applications of energy conversion as well as ionic diodes. Inspired by biological cells, we theoretically investigate for the first time the gate modulation of ion transport and selectivity in the soft nanochannel functionalized with biomimetic, pH-tunable, zwitterionic polyelectrolyte (PE) brush layers. The gate effect on the modulation of Donnan potential, ionic conductance, and ion selectivity in the biomimetic soft nanochannel is remarkable when the background salt concentration is low, pH is close to the isoelectric point of PE brush layers (slightly acidic), and the grafting density of PE brushes on the channel wall is small. Under those conditions, the biomimetic gated soft nanochannel is capable of being highly cation-selective when a negative gate voltage is applied. The findings provide a novel way for designing nanofluidic devices used in osmotic energy conversion and ion current rectification.

Direct observation of polyelectrolyte brushes under wet and dry conditions by atmospheric scanning electron microscopy.

Polyelectrolyte brushes are polyelectrolyte polymers with one end fixed to a substrate. In this study, direct nano-scale visualization of polyelectrolyte brushes was carried out under 'aqueous conditions' by atmospheric scanning electron microscopy. The thickness of the polyelectrolyte brush layer was measured under both dry and aqueous conditions, experimentally confirming the swollen state of the brushes. These experimental findings qualitatively agreed with the results from previous neutron reflectivity experiments using similar polyelectrolyte brushes. Such direct visualization of polymer brushes in real space opens up a new route for better understanding their surface properties, such as friction, adhesion and wettability.

Viscosity Modulation by Magnetic Field for Colloidal Polyelectrolyte Brushes

Aqueous dispersions of magnetic spherical polyelectrolyte brushes (MSPB) are prepared by mini‐emulsion followed by photo‐emulsion polymerization. Their viscosity increases dramatically upon increasing the intensity of an external magnetic field, showing the “magnetoviscous effect.” Unlike general magnetic nano‐particles, the increase in viscosity of MSPB cannot be described by Shliomis's theory, probably due to the covering of a spherical polyelectrolyte brush layer. MSPB rheology is also tunable by pH, and the brushes can stay in atmospheric conditions for months without changes in particle size and size distribution, which should make them ideal candidates for a broad range of industrial applications. The future applications of our multifunctional magnetic responsive system are promising.