A series of micro/nano capsules of polystyrene(PS)/tetracosane(C24)-octadecane(C18) eutectic mixture were synthesized as encapsulated phase change material (PCM) using emulsion polymerization method. The encapsulated PCMs were characterized chemically using FT-IR spectroscopy. The surface morphology and particle size of the synthesized capsules were investigated POM, SEM and PSD techniques. The results proved that the surfaces of the capsules had not completely spherical appearances and bimodal particle size distributions changed within 0.01-115 mu m. The thermal characteristics measured using DSC and TGA techniques indicated that the capsules containing highest amount of the eutectic mixture had a melting temperature of 25.96 degrees C, latent heat of 156.39 J g(-1) and high thermal durability. The thermal cycling test confirmed that the PS/(C24 C18) micro/nano capsules with 1:2 shell/core ratio had good thermal reliability after 5000 thermal cycling number. Furthermore, the synthesized PS/(C24 C18)(1:2) micro/nano capsules had a considerable high thermal conductivity. By taking account of all results, it can be drawn a conclusion that especially PS/(C24 C18)(1:2) micro/nano capsules can be considered as promising encapsulated PCM for low-temperature latent heat thermal energy storage applications. (C) 2015 Elsevier Ltd. All rights reserved.