Ionic Strength-Dependent Assembly of Polyelectrolyte-Nanoparticle Membranes via Interfacial Complexation at a Water–Water Interface

Abstract

Complexation between oppositely charged nanoparticles (NPs) and polyelectrolytes (PEs) is a scalable approach to assemble functional, stimuli-responsive membranes. Complexation at interfaces of aqueous two-phase systems (ATPSs) has emerged as a powerful method to assemble these functional structures. Membranes formed at these interfaces can grow continuously to thicknesses approaching several millimeters and display a high degree of tunability via modification of solution properties such as ionic strength. To identify the membrane assembly mechanism, we study interfacial assembly in a prototypical dextran/PEG ATPS, in which silica (SiO2) NPs suspended in the PEG phase undergo interfacial complexation with poly(diallyldimethylammonium chloride) (PDADMAC) supplied in the dextran phase. Using a microfluidic device that facilitates sequential insertion of fluorescent and nonfluorescent PDADMAC, we observe a transition in the membrane growth mechanism with ionic strength. In the absence of added salt ([NaCl] = 0 mM) PDADMAC chains permeate through the existing membrane to complex with NPs on the PEG side of the membrane, leading to the formation of well-stratified structures. At elevated ionic strength ([NaCl] = 500 mM), this permeation mechanism is lost. Rather, the complexing species incorporate uniformly across the membrane. We attribute this transition to a rapid exchange of PE-counterion, NP-counterion, and PE/NP binding sites facilitated by an increase in extrinsically compensated charged groups on the NPs and PEs at high salinity. These PDADMAC/SiO2 NP membranes have tremendous potential for the formation of functional membranes, offering control over the internal structure and serving as an ideal system for the generation of targeted release systems.

Optical Actuation of Nanoparticle-Loaded Liquid–Liquid Interfaces for Active Photonics

“…For instance, interfaces laden with silver nanoparticles can be readily prepared using the same thiol ligands that facilely bind to soft metals (Figure S18). Furthermore, the ability to manipulate particles at the interface presents opportunities for interfacial material manufacturing − and handling . The trapping capability applies to various sizes (2–10 μm) and other materials, including silica and iron oxide/PS (Movie S6).…”

Interfacial stabilization of aqueous two-phase systems: a review

“…128 Complexation of oppositely charged polyelectrolytes (PEs) or nanoparticles to form a shell around the droplet that maintains high rigidity and permeability can also serve as a stabilization mechanism. 56,130,[138][139][140] This approach accomplishes both goals of droplet stability and permeability while using inorganic materials. Biomolecules, such as proteins, carbohydrates, DNA, and even whole cells, have also been employed to stabilize PEG-dextran emulsions.…”

Nanocomposite colloids prepared by the Ouzo effect

“…Several strategies have been developed to facilitate the precise placement of nanoparticles within nanocolloids, either in the core or at the interface [3][4][5][10][11][12][13][14][15]. For example, nanoparticles have been successfully encapsulated by growing shells of various materials around the particles [3].…”

“…Additionally, nanoparticles have been successfully embedded in the pores of porous structures [3] or encased in various materials such as polymers or oils via emulsion polymerization [4,5]. The interfacial organization of nanoparticles has been achieved by producing Pickering emulsions with micro and nano-scale droplets [10][11][12][13] and performing layer-by-layer assembly of nanoparticles and polyelectrolytes on colloidal supports [14,15]. Despite these notable achievements in controlling the spatial arrangement of INPs in nanocolloids, most existing methods are restricted to producing nanocolloids with specific morphologies; that is, few approaches are able to regulate the location of nanoparticles from the core to the interface using the same methodology [3][4][5][10][11][12][13][14][15].…”

“…The interfacial organization of nanoparticles has been achieved by producing Pickering emulsions with micro and nano-scale droplets [10][11][12][13] and performing layer-by-layer assembly of nanoparticles and polyelectrolytes on colloidal supports [14,15]. Despite these notable achievements in controlling the spatial arrangement of INPs in nanocolloids, most existing methods are restricted to producing nanocolloids with specific morphologies; that is, few approaches are able to regulate the location of nanoparticles from the core to the interface using the same methodology [3][4][5][10][11][12][13][14][15]. Moreover, many of these methods rely on intricate and/or time-consuming processes, posing challenges to the scalable manufacturing of functional nanocolloids [3][4][5][10][11][12][13][14][15].…”