Probing the Mechanism of Targeted Delivery of Molecular Surfactants Loaded into Nanoparticles after Their Assembly at Oil-Water Interfaces

Equilibrium and self-assembly of Janus particles at liquid-liquid interfaces for the film formation

This article investigates the equilibrium arrangement, self-assembly process, and subsequent curing of amphiphilic snowman-shaped Janus particles at the oil-water interface. The independent Janus particles are in vertical equilibrium state and the contact position of the oil-water interface is at the largest cross section of the particle's hydrophobic phase. Under the effect of the surface tension and the adsorption of materials, Janus particles may form particle combinations including the particle pairs and the particle triangle, whose inner and outer sides have the liquid surface exhibiting completely opposite contact angles. Particle combinations form stable parallel double-chain structures with diverse shapes after the self-assembly process. However, the single Janus particles attain a state of mechanical equilibrium under the influence of surrounding particles, enabling them to assemble into regular array structures. The relationship of interfacial tension coefficient between phases can be changed by adjusting the oil-water system, which leads to variations in the self-assembly speed and the final arrangement results. The thin-film with uniformly distributed vertical particles is achieved by replacing the underlying deionized water with a curing agent. Based on the understanding of the interactions between irregularly shaped Janus particles at the oil-water interface, it will be convenient to achieve the controllable self-assembly and widely applications of these particles.

Building Functional Liquid-Based Interfaces: From Mechanism to Application

Functional liquid-based interfaces, with their inhomogeneous regions that emphasize the functionalized liquids, have attracted much interest as a versatile platform for a broad spectrum of applications, from chemical manufacturing to practical uses. These interfaces leverage the physicochemical characteristics of liquids, alongside dynamic behaviors induced by macroscopic wettability and microscopic molecular exchange balance, to allow for tailored properties within their functional structures. In this Minireview, we provide a foundational overview of these functional interfaces, based on the structural investigations and molecular mechanisms of interaction forces that directly modulate functionalities. Then, we discuss design strategies that have been employed in recent applications, and the crucial aspects that require focus. Finally, we highlight the current challenges in functional liquid-based interfaces and provide a perspective on future research directions.

Synthesis of Raspberry-like Nanoparticles via Surface Grafting of Positively Charged Polyelectrolyte Brushes: Colloidal Stability and Surface Properties

A method to synthesize stable, raspberry-like nanoparticles (NPs), using surface grafting of poly(glycidyl methacrylate) (PGMA) brushes on a polystyrene (PS) core with varying grafting densities, is reported. A two-step functionalization reaction of PGMA epoxide groups comprising an amination step first using ethylene diamine and then followed by a quaternization using glycidyltrimethylammonium chloride generates permanently and positively charged polyelectrolyte brushes, which result in both steric and electrostatic stabilization. The dispersion stability of the brush-bearing NPs is dramatically improved compared to that of the pristine PS core in salt solutions at ambient (25 °C) and elevated temperatures (60 °C). Additionally, the grafted polyelectrolyte chains undergo a reversible swelling in the presence of different ionic strength (IS) salts, which modulate the surface properties, including roughness, stiffness, and adhesion. An atomic force microscope under both dry and wet conditions was used to image conformational changes of the polyelectrolyte chains during the swelling and deswelling transitions as well as to probe the nanomechanical properties by analyzing the corresponding force-sample separation curves. The quaternized polyelectrolyte brushes undergo a conformational transition from a collapsed state to a swelled state in the osmotic brush (OB) regime triggered by the osmotic gradient of mobile ions to the interior of the polymer chain. At IS ∼ 1 M, the brushes contract and the globules reform (salted brush state) as evidenced by an increase in the surface roughness and a reduction in the adhesion of the brushes. Beyond IS ∼ 1 M, quartz crystal microbalance with dissipation monitoring measurements show that salt uptake continues to take place predominantly on the exterior surface of the brush since salt adsorption is not accompanied by a size increase as measured by dynamic light scattering. The study adds new insights into our understanding of the behavior of NPs bearing salt-responsive polyelectrolyte brushes with adaptive swelling thresholds that can ultimately modulate surface properties.