Tunable Pickering Emulsions with Environmentally Responsive Hairy Silica Nanoparticles

Abstract

Surface modification of the nanoparticles using surface anchoring of amphiphilic polymers offers considerable scope for the design of a wide range of brush-coated hybrid nanoparticles with tunable surface wettability that may serve as new class of efficient Pickering emulsifiers. In the present study, we prepared mixed polymer brush-coated nanoparticles by grafting ABC miktoarm star terpolymers consisting of poly(ethylene glycol), polystyrene, and poly[(3-triisopropyloxysilyl)propyl methacrylate] (μ-PEG-b-PS-b-PIPSMA) on the surface of silica nanoparticles. The wettability of the as-prepared nanoparticles can be precisely tuned by a change of solvent or host-guest complexation. H NMR result confirmed that such wettability change is due to the reorganization of the polymer chain at the grafted layer. We show that this behavior can be used for stabilization and switching between water-in-oil (W/O) and oil-in-water (O/W) emulsions. For hairy particles initially dispersed in oil, W/O emulsions were always obtained with collapsed PEG chains and mobile PS chains at the grafted layer. However, initially dispersing the hairy particles in water resulted in O/W emulsions with collapsed PS chains and mobile PEG chains. When a good solvent for both PS and PEG blocks such as toluene was used, W/O emulsions were always obtained no matter where the hairy particles were dispersed. The wettability of the mixed polymer brush-coated silica particles can also be tuned by host-guest complexation between PEG block and α-CD. More importantly, our result showed that surprisingly the resultant mixed brush-coated hairy nanoparticles can be employed for the one-step production of O/W/O multiple emulsions that are not attainable from conventional Pickering emulsifiers. The functionalized hairy silica nanoparticles at the oil-water interface can be further linked together utilizing poly(acrylic acid) as the reversible linker to form supramolecular colloidosomes, which show pH-dependent release of cargo.

Hybrid Silicon‐Based Organic/Inorganic Block Copolymers with Sol–Gel Active Moieties: Synthetic Advances, Self‐Assembly and Applications in Biomedicine and Materials Science

“…The diblock copolymer macroinitiator, namely PEO‐(Br)‐ b ‐PS, was synthesized via the esterification of PEO‐(OH)‐ b ‐PS with 2‐bromoisobutyryl bromide in dichloromethane and the PEO‐(OH)‐ b ‐PS diblock copolymers bearing hydroxyl group on the junction point had been previously synthesized by the click reaction between a PEO bearing an azide and hydroxyl group and an α‐alkynyl‐ω‐diethylamino‐polystyrene. The miktoarm μ‐PEO 45 ‐ b ‐PS 25‐86 ‐ b ‐PIPSPMA 25‐35 triblock copolymers were obtained with relatively low dispersities of 1.22–1.27 and a molar mass of up to 22.5 kDa . Pan and co‐workers prepared H‐shaped PEO‐ b ‐PTMSPMA copolymers by using a multifunctional Br 2 ‐PEO‐Br 2 macroinitiator .…”

“…The group of Chen synthesized as eries of linear amphiphilic diblock poly(ethylene oxide)-b-poly [3-(trimethoxysilyl) propyl methacrylate] (PEO-b-PTMSPMA) copolymers by employing CuBr/PMDETAm ediated ATRP of TMSPMA in anisole at 50, 70 or 90 8Cf rom variousP EO-Br macroinitiators:P EO 17 42,49,54,59,180 or PEO 113 -b-PTMSPMA 46,206 . [41] To obtain this macroinitiator, poly(ethylene oxide)m ethoxyetherw as functionalized at the chain-endw ith 2-bromo-2-methylpropionylb romide to afford poly(ethylene oxide)2 -bromo-2-methylpropionate (PEO-Br).…”

“…The miktoarm m-PEO 45 -b-PS 25-86 -b-PIPSPMA [25][26][27][28][29][30][31][32][33][34][35] triblock copolymers were obtained with relatively low dispersities of 1.22-1.27 and am olarm ass of up to 22.5 kDa. [46] Pan and co-workersp repared H-shaped PEO-b-PTMSPMA copolymers by using am ultifunctional Br 2 -PEO-Br 2 macroinitiator. [47] They obtained well-definedH -shaped (PTMSPMA 98,154,182 ) 2 -b-PEO 91 -b-(PTMSPMA 98,154,182 ) 2 copolymers with dispersities of 1.05-1.17 and am olar mass of up to % 50 kDa by employing CuBr/bpy mediated ATRP in methanol at room temperature.…”

“…Concerning the first approach, Ngai and co-workers used silica nanoparticles (21 nm) coated with miktoarm m-PEO 45 -b-PS 25-86 -b-PIPSPMA [25][26][27][28][29][30][31][32][33][34][35] triblock copolymers as Pickering emulsifiers ( Figure 8a). [46] For the hairy nanoparticles grafted with m-PEO 45 -b-PS 25 -b-PIPSPMA 25 ,w hen they were initially dispersed in oil, W/O emulsions werea lwayso btained with particles having collapsed PEO chains but mobile PS chains, while by initially dispersing the particlesi nw ater,O /W emulsions resulted, where the hairy particles had collapsed PS chains and mobile PEO chains. When ag ood solvent for both PS and PEOb locks such as toluene was used, W/O emulsions were always obtained no matter where the hairy particles were dispersed.…”

Effect of Pickering emulsion on the mechanical performances and fracture toughness of epoxy composites

“…Pickering emulsion, which is stabilized by ultrafine particles (for example colloidal silica) of sizes from a few nanometers to hundreds of micrometers, 27 has attracted widespread interest in areas such as pharmaceutics, 27,28 high-performance polymer nanocomposites, 29,30 environment protection, 31,32 phase change materials, 33 and functional materials. 34,35 Some of the used stabilized particles are nanocelluloses, 29,36 TiO 2,35 cellulose nanocrystals, 30,37 and silica nanoparticles.…”