A Facile One-Step Approach toward Polymer@SiO₂ Core–Shell Nanoparticles via a Surfactant-Free Miniemulsion Polymerization Technique

Abstract

We present a surfactant-free miniemulsion process for the preparation of monodisperse polystyrene@SiO2 nanoparticles with a well-defined core–shell structure. The strategy utilizes a silica precursor polymer, hyperbranched polyethoxy­siloxane (PEOS), as a sole miniemulsion stabilizer due to its water insolubility and at the same time pronounced amphiphilicity induced by hydrolysis at the oil/water interface. The core–shell particles are obtained by emulsifying a PEOS/styrene mixture in water and subsequent heating to initiate polymerization. As the polymerization proceeds, driven by osmotic pressure and incompatibility with polystyrene, PEOS macromolecules migrate continuously toward the oil/water interface where sol–gel reaction takes place. As soon as the polymerization is completed, PEOS is fully expelled from the polymer phase and is converted to silica on the polystyrene surface. This method allows an easy control of silica shell thickness by varying the PEOS concentration. The particle size, on the other hand, can be regulated not only by the shearing force but also by the pH of the aqueous medium. This process offers a new type of miniemulsion polymerization technique for the preparation of composite polymer particles that is facile, low cost, highly scalable, and environmentally friendly.

Hybrid nanostructured particles via surfactant-free double miniemulsion polymerization

“…During this process, the particle size and size distribution of the double emulsion decrease, and they reach a plateau (mean diameter 515 nm, PDI 0.14) after 6 h. Since the resulting nanocapsules resemble the structure of the droplets and the creation of monomer swollen micelles as in the case of classical emulsion polymerization is not observed, the polymerization in the present system seems to be confined in the double emulsion droplets and proceeds according to a miniemulsion polymerization mechanism. The significant size decrease can be accounted for by the polymerization-induced shrinkage and for the most part by the conversion of PEOS to silica, which is accompanied by at least 50% weight loss 25 .…”

“…Recently, we reported the formation of O/W miniemulsions by emulsifying a solution of a silica precursor polymer, hyperbranched polyethoxysiloxane (PEOS) 23 , in a hydrophobic liquid in water 24 , 25 . PEOS is a water-insoluble liquid, which becomes amphiphilic upon hydrolysis at the oil/water interface.…”

“…The interfacial tension between a styrene solution containing PEOS and water of pH 7 reaches with time the final value as low as 10 mN/m that is only 1/3 of the value between pure styrene and water. Monodisperse polystyrene@SiO 2 core-shell nanoparticles were prepared via miniemulsion polymerization of the styrene/PEOS-in-water system 25 . Since the amphiphilicity of PEOS is induced by hydrolysis at the oil/water interface, PEOS should in principle also be able to stabilize W/O emulsions.…”

Deformation of raspberry-like polymer composite particles by colloidal fusion

“…Since the pioneering work by Armes in the 1990s, [1][2][3] much attention has been devoted to the synthesis of colloidal polymer composite particles with defined morphology, which is usually critical to tune their physical and chemical properties. 4,5 The most commonly reported morphologies include core-shell [6][7][8][9][10][11][12] and raspberry-like morphologies. As the name suggests, a raspberry-like polymer composite particle refers to a particle consisting of smaller corona particles attached to the surface of a larger core particle (including inorganic-polymer, polymerinorganic, and polymer-polymer core-corona structures).…”

Synthesis and Assembly of Gold and Iron Oxide Particles Within an Emulsion Droplet; Facile Production of Core@Shell Particles

“…The contact angle of the particle at the interface can be controlled and can be used to create oil-inwater or water-in-oil emulsions, known generally as Pickering Emulsions. Pickering emulsion synthesis strategies have assembled a range of both polymer and inorganic materials at the interface of the droplets [16][17][18][19], and when materials are present in both phases even core@shell particles can be synthesised [20]as shown in Fig. 1 iii.…”