Abstract
Janus particles exhibit a strong tendency to directionally assemble and segregate to interfaces and thus offer advantages as colloidal analogues of molecular surfactants to improve the stability of multiphasic mixtures. Investigation and application of the unique adsorption properties require synthetic procedures that enable careful design and reliable control over the particles’ asymmetric chemistry and wettability profiles with high morphological uniformity across a sample. Herein, we report on a novel one-step synthetic approach for the generation of amphiphilic polymer Janus particles with highly uniform and tunable wettability contrasts, which is based on using reconfigurable bi-phasic Janus emulsions as versatile particle scaffolds. Two phase-separated acrylate oils were used as the constituent droplet phases and transformed into their solidified Janus particle replicas via UV-induced radical polymerization. Using Janus emulsions as particle precursors offers the advantage that their internal droplet geometry can be fine-tuned by changing the force balance of surface tensions acting at the individual interfaces via surfactants or the volume ratio of the constituent phases. In addition, preassembled functional surfactants at the droplet interfaces can be locked in position upon polymerization, which enables both access toward postfunctionalization reaction schemes and the generation of highly uniform Janus particles with adjustable wettability profiles. Depending on the particle morphology and wettability, their interfacial position can be adjusted, which allows us to stabilize either air bubbles-in-water or water droplets-in-air (liquid marbles). Motivated by the interfacial activity of the particles and particularly the longevity of the resulting particle-stabilized air-in-water bubbles, we explored their ability to promote the delivery of oxygen inside a liquid-phase reaction medium, namely, for the heterogeneous Au-NP-mediated catalytic oxidation of d-glucose. We observed a 2.2-fold increase in the reaction rate attributed to the increase of the local concentration of oxygen around catalysts, thus showcasing a new strategy to overcome the limited solubility of gases in aqueous reaction media.
Highlights
IntroductionJanus particles represent a unique collection of functional hybrid materials because they provide asymmetry and can impart different chemical or physical properties and directionality within a single-particle system.[1,2] Due to unique amphiphilic, magnetic, catalytic, optical, or electrical properties, Janus particles can possess advantages over their singlecomponent counterparts with implications for a wide range of applications in the fields of physics, chemistry, and biological science.[3,4] As such, Janus particles have been used as colloidal building blocks for self-assembled structure formation,[5,6] in optics and imaging applications,[7,8] and as motile particles with directional propulsion profiles,[9,10] transducers and signal amplifiers in sensing applications,[11,12] and powerful solid surfactants that allow us to control and influence the packing dynamics at interfaces.[13,14]Amphiphilic Janus particles can mediate superior stability to multiphasic mixtures, such as emulsions, foams, or polymer blends, as opposed to their homogeneous counterparts.[15]
To create Janus particles in various morphologies, we started with the generation of the Janus emulsion molds composed of a 1:1 volume mixture of hydrocarbon and fluorocarbon monomers, namely, 1,6 hexanediol diacrylate (HDDA) and perfluorodecyl acrylate (PFDA)
In this article, we demonstrated a novel approach for the generation of functional spherical polymer Janus particle with tunable amphiphilicities, using reconfigurable biphasic Janus emulsions as versatile particle scaffolds
Summary
Janus particles represent a unique collection of functional hybrid materials because they provide asymmetry and can impart different chemical or physical properties and directionality within a single-particle system.[1,2] Due to unique amphiphilic, magnetic, catalytic, optical, or electrical properties, Janus particles can possess advantages over their singlecomponent counterparts with implications for a wide range of applications in the fields of physics, chemistry, and biological science.[3,4] As such, Janus particles have been used as colloidal building blocks for self-assembled structure formation,[5,6] in optics and imaging applications,[7,8] and as motile particles with directional propulsion profiles,[9,10] transducers and signal amplifiers in sensing applications,[11,12] and powerful solid surfactants that allow us to control and influence the packing dynamics at interfaces.[13,14]Amphiphilic Janus particles can mediate superior stability to multiphasic mixtures, such as emulsions, foams, or polymer blends, as opposed to their homogeneous counterparts.[15]. An Received: April 20, 2021 Accepted: June 18, 2021 Published: June 29, 2021
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