Synthesis of dimpled polymer-silica nanocomposite particles by interfacial swelling-based seeded polymerization

Dimpled polymer-silica nanocomposite particles have the combined advantages of dimpled particles and polymer-silica nanocomposite particles. This study presents a novel approach to prepare these particles by interfacial swelling-based seeded polymerization. Polystyrene-silica (PS-SiO2) nanocomposite particles are first prepared by emulsion polymerization of styrene in the presence of glycerol-functionalized silica sols and then dimpled polymer-SiO2 particles are fabricated by interfacial swelling of butyl acrylate (BA)/toluene and subsequent seeded polymerization of BA with the PS-SiO2 particles as seeds. The effects of different parameters, such as the amount of surfactant used in the PS-SiO2/H2O dispersion, BA/toluene mass ratio, PS-SiO2/H2O mass ratio and stirring rate, on the formation of the dimpled particles are investigated. Optimization of the seeded polymerization conditions allows a relatively high percentage of dimpled particles to be achieved.

Synthetic strategies for raspberry-like polymer composite particles

The strategies used for the preparation of raspberry-like polymer composite particles are summarized comprehensively.

Double in Situ Preparation of Raspberry-like Polymer Particles

Well-defined raspberry-like poly(styrene- co-4-vinylpyridine)-SiO₂ nanocomposite particles with a diameter of around 200 nm were easily prepared by a double in situ process in nanoemulsion with the water-soluble dye Eosin Y as the stabilizer. During radical polymerization of the nanodroplets comprising styrene, 4-vinylpyridine (4-VP), and tetraethoxysilane (TEOS), the silane phase is expelled from the polymer phase to the oil/water (o/w) interface. In the later polymerization stage, SiO₂ nanoparticles with a size of around 25 nm were produced via the in situ sol-gel reaction of TEOS at the o/w interface promoted by the negatively charged dye. The pyridine moieties in the copolymer fix the SiO₂ nanoparticles on the surface of the polymer particles by electrostatic interactions without any sign of free unbound silica particles as proven by transmission electron microscopy.

Polymeric raspberry-like particles via template-assisted polymerisation

Functional monodisperse raspberry-like colloids are fabricated via template-assisted polymerisation, leading to optical materials with high dispersion stability in an aqueous environment.

Preparation of Dimpled Polystyrene-Silica Colloidal Nanocomposite Particles

Preparation of polymer-silica colloidal nanocomposite particles with concave shape is challenging and seldom reported. This paper presents a novel and facile method to prepare dimpled polymer-silica nanocomposite particles with a thin silica shell through the judicious combination of alcoholic dispersion polymerization and the decane evaporation method. Submicrometer-sized polystyrene-silica (PS-SiO₂) nanocomposite particles were first prepared by dispersion polymerization of styrene in methanol in the presence of a methanolic silica sol, and then dimpled PS-SiO₂ particles were prepared by heating the near-spherical PS-SiO₂ particles dispersed in methanol/water media in the presence of decane and subsequent cooling. The effects of different heat treatment parameters, such as methanol/water ratio, stirring temperature, and stirring rate on the formation of the nanocomposite particles were investigated. Optimization of the heating conditions allowed ∼100% of dimpled particles to be achieved with one dimple on each particle. Moreover, calcination of the dimpled PS-SiO₂ nanocomposite particles led to the formation of hollow dimpled particles with a thin silica shell. This method is expected to enrich the shapes of polymer-silica nanocomposite particles.

Adsorption of Silica Nanoparticles onto Poly(N-vinylpyrrolidone)-Functionalized Polystyrene Latex

This paper presents a more general method to prepare silica-coated polystyrene (PS) particles with minimal excess silica by adsorption, highlighting the role of poly(N-vinylpyrrolidone) (PVP). The method is based on the addition of small silica nanoparticles onto submicrometer-sized near-monodisperse polymer latex particles under the conditions of monolayer silica coverage of the latex surface. Either a cationic or an anionic initiator could be used in the PVP-involved emulsion polymerization to prepare PS particles, and the adsorption was conducted successfully either under acidic or basic conditions. Neither a cationic initiator nor a basic condition is a prerequisite for the adsorption process, which should be related to the much stronger interaction between PVP and the silica surface. This method is expected to substantially extend the adsorption conditions of polymer-silica colloidal nanocomposite syntheses.

Ionic liquid based microemulsion method for the fabrication of poly(methyl methacrylate)–TiO2 nanocomposite as a highly efficient visible light photocatalyst

A novel PMMA/TiO₂/IL photocatalyst has been prepared and its photocatalytic activity was evaluated for the degradation of MB dye under visible light.

Physical adsorption of anisotropic titania nanoparticles onto poly(2-vinylpyridine) latex and characterisation of the resulting nanocomposite particles

Four poly(2-vinylpyridine) latexes with intensity-average mean diameters ranging between 246 and 955nm were prepared by aqueous emulsion polymerisation. These latexes were characterised by transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, aqueous electrophoresis, disc centrifuge photosedimentometry and thermogravimetry. The adsorption of rice grain-shaped nano-sized titania particles onto the surface of these latex particles from aqueous solution was investigated. It was found that the titania particles adsorb strongly at pH 10 and the optimal loading and packing density of titania was investigated for each latex. The resulting core-shell P2VP-titania nanocomposite particles were characterised in terms of their titania contents, surface coverages and colloidal stabilities. UV-Vis spectra were recorded for the titania nanoparticles, the original P2VP latexes and the poly(2-vinylpyridine)-titania nanocomposite particles. It was found that, for the larger nanocomposite particles, UV-Vis absorption was dominated by the latex core, whereas the smaller P2VP-titania nanocomposite particles exhibited UV attenuation to longer wavelengths compared to both the bare latex and the titania particles. The poly(2-vinylpyridine) cores were selectively removed by calcination of the nanocomposite particles and the resulting hollow titania structures were investigated by transmission electron microscopy.