Core-shell-structured silica/polyacrylate particles prepared by Pickering emulsion: influence of the nucleation model on particle interfacial organization and emulsion stability.

Jing Ji,Shi Shu,Yi Jia,Feng Wang,Jingjun Liu,Zhilin Li,Ye Song

doi:10.1186/1556-276x-9-534

Jing Ji, Shi Shu + Show 5 more

Open Access

https://doi.org/10.1186/1556-276x-9-534

Copy DOI

Abstract

This work reports a new evidence of the versatility of silica sol as a stabilizer for Pickering emulsions. The organization of silica particles at the oil-water interface is a function of the nucleation model. The present results show that nucleation model, together with monomer hydrophobicity, can be used as a trigger to modify the packing density of silica particles at the oil-water interface: Less hydrophobic methylmethacrylate, more wettable with silica particles, favors the formation of core-shell-structured composite when the composite particles are prepared by miniemulsion polymerization in which monomers are fed in batch (droplet nucleation). By contrast, hydrophobic butylacrylate promotes the encapsulating efficiency of silica when monomers are fed dropwise (homogeneous nucleation). The morphologies of polyacrylate-nano-SiO2 composites prepared from different feed ratio of methylmethacrylate/butylacrylate (with different hydrophobicity) and by different feed processes are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The results from SEM and TEM show that the morphologies of the as-prepared polyacrylate/nano-SiO2 composite can be a core-shell structure or a bare acrylic sphere. The stability of resulting emulsions composed of these composite particles is strongly dependent on the surface coverage of silica particles. The emulsion stability is improved by densely silica-packed composite particles.

Highlights

Since the emulsion stabilized by only fine solid particles, as described in 1907 [1], these so-called Pickering emulsions have been obtained with a wide variety of organic or mineral powders [2,3,4,5,6,7,8,9,10,11,12]
Inspired by the works of Hey [24], we investigate the effects of the glass-transition temperature Tg of growing polymer particles and the monomer mixture hydrophobicity on the anchorage of silica particles in the polymer by varying the mass ratio of methyl merthacrylate (MMA)/butyl acrylate (BA)
In summary, core-polyacrylate/shell-silica nanocomposite particles are synthesized by simple soap-free emulsion polymerization employing negatively charged silica sol

Summary

Introduction

Since the emulsion stabilized by only fine solid particles, as described in 1907 [1], these so-called Pickering emulsions have been obtained with a wide variety of organic or mineral powders [2,3,4,5,6,7,8,9,10,11,12]. Arditty et al [23] indicated that the surface coverage of particles increased with the increasing of the mixing intensity They used different oils, with the viscosities ranging from 10 to 350 cP, to prepare the solidstabilized emulsions, but found no apparent effect of o/w ratio on the generation of the emulsions. The experiment showed that the use of monomers that had high water solubility and was prone to hydrolyze under basic conditions would result in complete microcoagulation, the use of small amounts of methacrylic acid as auxiliary monomer promoted clay adhesion to the surface of the particles in the Pickering emulsion (co) polymerization of hydrophobic monomers

Methods

Results

Conclusion