We propose a novel route for the stabilization of oil-in-water Pickering emulsions using inherently hydrophilic nanoparticles. In the case of dialkyl adipate oils, in situ hydrophobisation of the particles by dissolved oil molecules in the aqueous phase enables stable emulsions to be formed. Emulsion stability is enhanced upon decreasing the chain length of the oil due to its increased solubility in the precursor aqueous phase. The oil thus acts like a surfactant in this respect in which hydrogen bonds form between the carbonyl group of the ester oil and the hydroxyl group on particle surfaces. The particles chosen include both fumed and precipitated anionic silica and cationic zirconia. Complementary experiments including relevant oil-water-solid contact angles and infra-red analysis of dried particles after contact with oil support the proposed mechanism.

Microcapsules with high thermal energy storage density were synthesized by in situ polymerization using melamineformaldehyde resin as shell and n-hexadecanol as core. Styrene-maleic anhydride (SMA) copolymer was synthesized by solution polymerization and hydrolyzed by NaOH to enhance its water solubility. This negatively charged SMA molecular copolymer self-assembles on the surface of n-hexadecanol droplets and facilitates the precipitation of positively charged melamine-formaldehyde prepolymer onto the droplet surface electrostatically. The morphology, chemical structure, composition, and thermal properties were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, and gas chromatography, respectively. The results show that the obtained microencapsulated phase-change material (MePCM) dispersed individually with a spherical shape. Amount of emulsifier, ratio of shell-core material, and pH value of solution have a significant effect on the microencapsulation. Under optimum condition of 8% SMA to core material, 3.3:10 of shell-core material in feed, and polymerization under pH 4.0, spherical n-hexadecanol MePCMs with core content of 79.1% and melting enthalpy of 171 J g À1 at around 51°C were prepared. In situ polymerization based on SMA-stabilized emulsion opens up a route to prepare a variety of microcapsules with aliphatic alcohol as core material.

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a Microencapsulated phase change materials (MePCMs) using melamine-formaldehyde resin/SiO 2 as shell were investigated in this paper. Organically modified SiO 2 particles were employed to stabilize Pickering emulsion, and in situ polymerization of melamine and formaldehyde was carried out to form hybrid shell. The performances of resultant MePCMs with hybrid shell were investigated comparatively with the MePCMs with polymer shell. SiO 2 particles raise the microencapsulation efficiency by improving the stability of emulsion and providing a precipitation site for melamine-formaldehyde resin. Also, the mechanical strength, thermal reliability, and anti-osmosis performance of MePCMs were improved significantly by SiO 2 particles in the shell. Our study shows that Pickering emulsion is a simple and robust template for MePCMs with polymer-inorganic hybrid shell.

Hollow microspheres with SiO 2 /polymer binary shell were fabricated from Pickering emulsion stabilized solely by methacryloxypropyltrimethoxysilane-modified SiO 2 particles, and were characterized by optical microscopy, scanning electron microscopy, Fourier transformation infrared spectrum, thermogravimetric analysis (TGA), and energy dispersive X-ray spectroscopy. The microspheres were templated by the Pickering droplets and the inner structure was affect by the proportion of crosslinking reagent. TGA result indicated that 60.3% of polymer in the shell was connected with SiO 2 by covalent bond which was formed by copolymerization of styrene and the reactive C --C group on SiO 2 stabilizer.