Polymer shell microcapsules with liquid cores are used in a wide variety of industries, from food and flavour protection to inkless paper. There is a number of production methods, each with different characteristics and this article reviews a number of them. The methods considered are colloidosome formation, polymer precipitation by phase separation, polycondensation interfacial polymerisation, layer-by-layer polyelectrolyte deposition, polymer growth by surface polymerisation and copolymer vesicle formation. Each production method is described and the relative strength of each is outlined.

This paper presents the formation of low temperature colloidosomes from colloidal poly(styrene-co-butyl acrylate) particles for both water-in-oil and oil-in-water systems. An investigation into the sintering conditions examines the ultimate shell morphology formed, with longer sintering times and higher sintering temperatures producing less porous microcapsules. This has been verified by the release of an encapsulated dye from the aqueous core microcapsules, in which slower release has been detected for longer sintering times. The results are subsequently fitted with a diffusion equation to give a diffusion coefficient of fluorescein through the polymeric shell of 10 -17 m 2 /s.

Currently, there is a resurgence of interest in the preparation of monodisperse, size-controlled latex particles in non-polar solvents by the dispersion polymerization technique. This technique has great potential for manufacturing bespoke latex particles for emerging applications such as the use of latex particles in electrophoretic displays, where one of the numerous requirements is that the particle systems be suspended in low dielectric constant, non-polar solvents. This article reviews the academic literature around the typical monomers used in non-polar dispersion polymerization. It briefly introduces the origin of the technique and the initial seminal work carried out in this area. It also describes how such particles have been used in the past as model colloids for academic purposes and provide recent examples where dispersion polymerization is used to create novel functional particles. Subsequently, the article provides a thorough knowledge basis for each monomer used in non-polar dispersion polymerization, with a focus on the evolution of the technique, including progress in controlling the final particle characteristics and in designing novel effective stabilizers. Finally, a brief review on the use of the technique to prepare well-controlled latex particles in supercritical fluids is also presented.

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Printing of droplets of pure solvents containing suspended solids typically leads to a ring stain due to convective transport of the particles toward the contact line during evaporation of the solvent. In mixtures of volatile solvents, recirculating cells driven by surface tension gradients are established that lead to migration of colloidal particles toward the center of the droplet. In favorable cases, a dense disk of particles forms with a diameter much smaller than that of the droplet. In the latter stages of drying, convective transport of the particles radially toward the contact line still occurs. Two strategies are described to fix the distribution of particles in a compact disk much smaller than the initial diameter of the drying droplet. First, a nanoparticulate clay is added to induce an evaporation-driven sol−gel transition that inhibits convective flow during the latter stages of drying. Second, a nonadsorbing polymer is added to induce depletion flocculation that restricts particle motion after the particles have been concentrated near the center of the droplet. The area of the resulting deposit can be as little as 10% of the footprint of the printed droplet.

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Latex films were dried on a flexible substrate, and the substrate deflection was monitored over time to give an averaged film stress-evolution profile. Films were dried at various temperatures below and above the minimum film-formation temperature of the latex dispersion. The effect of polymer rheology, which is a temperature-dependent parameter, on film formation, was investigated. The reliability of the Stoney model in predicting film stress from substrate curvature was also examined and compared to the Euler-Bernoulli model. It was shown that the linearized Stoney model was unsuitable for the larger measured stresses.