Janus Nanoparticles with Tunable Amphiphilicity for Stabilizing Pickering-Emulsion Droplets via Assembly Behavior at Oil–Water Interfaces

Abstract

Janus particles (JNPs) with controlled anisotropies are regarded as promising materials for sophisticated building blocks and assembly. Herein a straightforward method was proposed for the synthesis of uniformly distributed JNPs with controllable anisotropies, showing two compartmental bulbs with different surface wettability. The synthetic strategy is based on the phase separation-induced styrene liquid protrusion on seed poly(styrene-co-acrylic acid) (CPSAA) nanoparticles via controlled swelling, with the formed polystyrene (PS) and CPSAA compartments corresponding to the amount of monomers. The size (lateral length) ratio of formed PS and CPSAA bulbs, D PS /D CPSAA , defined as "Janusity", has been precisely tuned in the range of 0−0.91 by controlling the mass ratio of two monomers. Obtained JNPs with tunable amphiphilicity are utilized as colloid surfactants to prepare Pickering-emulsions of both water-in-oil (W/O) and oil-in-water (O/W) with proper Janusity. The stability of achieved W/O and O/W Pickering-emulsions is dependent on the adhesion energy of a JNP at the water−oil interfaces. Prepared JNPs have also being utilized to prepare and stabilize monodisperse droplets in microfluidic devices, demonstrating their high potential for fundamental research and practical applications.

Preparation of water-dispersible Janus nanosheets from K4Nb6O17·3H2O and their behaviour as a two-dimensional surfactant on air–water and water-toluene interfaces

“…The repeating distance of PPA_NbO was closely similar to that of A-type PPA_NbO in our previous study. 26 Assuming that PPA_PA_NbO is also an A-type derivative, where two different interlayers appear alternately in the stacking direction, 25 the repeating distance is calculated to be 3.60 nm, that is a doubled sum of the sizes of the PPA moiety, 0.63 nm, 17 Based on these data, the reaction seemed to proceed through the following steps. First, surface modification using PPA at interlayer I was achieved by using the A-type intercalation compound described in our previous report; an A-type organophosphonate derivative can be obtained from an A-type intercalation compound, since organophosphonic acid reacted only at interlayers expanded by ammonium ions.…”

“…13 Janus nanoparticles with individual hydrophobic and hydrophilic surfaces also exhibited surface activity. Gold, 14 silica, 15,16 and block copolymers 17 based Janus nanoparticles showed surface activity and a stabilized emulsion. In the history of surfactants, Janus nanosheets are attracting attention as a new category of surfactants due to their unique twodimensional structures.…”

From shaping to functionalization of micro-droplets and particles

“…219 Particularly, the various methods of making colloidal surfactants with biocompatible materials have been introduced. [220][221][222] Thus, biocompatible and less toxic colloidal surfactants could be able to replace conventional chemical surfactants and achieve water purication in an environmentally friendly manner. Hydrogel microcapsules composed of photocatalytic nanoparticles exhibit unique properties, including permeation, purication, and the catalytic reaction of molecular species.…”

Advances in the use of microgels as emulsion stabilisers and as a strategy for cellulose functionalisation

“…It has been shown that the same microgel particles can act as stabilisers for both W/O and O/W systems, where the emulsion type is controlled through water-oil ratio, emulsification conditions and microgel concentration (Fujii et al 2006;Brugger et al 2008). The ability to control the stability and type of emulsion formed is important in many processes such as oil extraction and recovery, heterogeneous and multiphase catalysis , food processing and drug delivery (Xie et al 2012(Xie et al , 2020. Using a single, ''multi-purpose'' stabiliser to fabricate emulsions with switchable behaviour could be hugely advantageous in many fields.…”