A simple model for the barrier properties of brushes with an arbitrary chain length distribution.

Polymer brushes can form protective barriers on surfaces, reducing fouling and adsorption of foreign entities. Predicting how the properties of such surfaces depend on physical brush parameters has technological implications for the applications of these coatings. However, most theoretical models require in-depth knowledge or advanced mathematical and computational skills, which prevents their broad use.

Responsive Polyelectrolyte Brushes in Applications: Functions, Stimuli, and Design Considerations.

Polyelectrolyte brushes are stimulus-responsive coatings that change surface properties such as friction, adhesion, and interaction with biomolecules. Brush coatings are becoming increasingly available with improving synthesis and fabrication methods, but their use in real-world applications is trailing behind. With their stimulus-controlled properties, brushes can fulfill a variety of functions when they are applied in a broad spectrum of use cases ranging from tunable lubrication to ionic current rectification.

Molecular Design Strategies to Enhance the Electroresponse of Polyelectrolyte Brushes: Effects of Charge Fraction and Chain Length Dispersity.

Polyelectrolyte brushes are functional surface coatings that react to external stimuli. The response of these brushes in electric fields is nearly immediate as the field acts directly on the charges in the polyion, while the response to bulk stimuli such as temperature, acidity, and ionic composition is intrinsically capped by transport limitations. However, the response of fully charged brushes is limited because large field strengths are required to achieve a response.

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 coarse-grained simulations and experiments, such interaction has not been studied in molecular detail.

Electrical Chain Rearrangement: What Happens When Polymers in Brushes Have a Charge Gradient?

Under the influence of electric fields, the chains in polyelectrolyte brushes can stretch and collapse, which changes the structure of the brush. Copolymer brushes with charged and uncharged monomers display a similar behavior. For pure polyelectrolyte and random copolymer brushes, the field-induced structure changes only the density of the brush and not its local composition, while the latter could be affected if charges are distributed inhomogeneously along the polymer backbone.

Electrostatic Fields Stimulate Absorption of Small Neutral Molecules in Gradient Polyelectrolyte Brushes.

Molecules can partition from a solution into a polymer coating, leading to a local enrichment. If one can control this enrichment via external stimuli, one can implement such coatings in novel separation technologies. Unfortunately, these coatings are often resource intensive as they require stimuli in the form changes of bulk solvent conditions such as acidity, temperature, or ionic strength.

Enhanced vapor sorption in block and random copolymer brushes.

Polymer brushes in gaseous environments absorb and adsorb vapors of favorable solvents, which makes them potentially relevant for sensing applications and separation technologies. Though significant amounts of vapor are sorbed in homopolymer brushes at high vapor pressures, at low vapor pressures sorption remains limited. In this work, we vary the structure of two-component polymer brushes and investigate the enhancement in vapor sorption at different relative vapor pressures compared to homopolymer brushes.

Vapor sorption in binary polymer brushes: The effect of the polymer-polymer interface.

Polymer brushes attract vapors that are good solvents for polymers. This is useful in sensing and other technologies that rely on concentrating vapors for optimal performance. It was recently shown that vapor sorption can be enhanced further by incorporating two incompatible types of polymers A and B in the brushes: additional vapor adsorbs at the high-energy polymer-polymer interface in these binary brushes.

Concentrating Vapor Traces with Binary Brushes of Immiscible Polymers.

Vapors in the air around us can provide useful information about our environment, but we need sensitive vapor sensors to access this information, especially because those vapors are often present at very low concentrations. We report molecular dynamics simulations of a concept that can significantly increase the sensitivity of vapor sensors at low concentrations. By coating the sensor surfaces with end-anchored immiscible polymers, surface-bound polymer blends are formed that can concentrate vapors, reaching sorption enhancements of more than one order of magnitude, especially at low vapor concentrations.

Friends, Foes, and Favorites: Relative Interactions Determine How Polymer Brushes Absorb Vapors of Binary Solvents.

Polymer brushes can absorb vapors from the surrounding atmosphere, which is relevant for many applications such as in sensing and separation technologies. In this article, we report on the absorption of binary mixtures of solvent vapors (A and B) with a thermodynamic mean-field model and with grand-canonical molecular dynamics simulations. Both methods show that the vapor with the strongest vapor-polymer interaction is favored and absorbs preferentially.