The microcapsules comprising n-octadecane and nucleating agents encapsulated in melamine-formaldehyde resin shell with about 1 mum in average diameter were prepared through in situ polymerization. The effects of nucleating agents, i.e. sodium chloride, 1-octadecnol and paraffin, on the crystallization properties, morphology and dispersibility of microcapsules were investigated using SEM, DSC and XRD. The super-cooling was prevented by adding about 6 wt.% sodium chloride to the emulsion, however, the microcapsules were worse dispersed and their surfaces were rough. Adding approximately 9 wt.% 1-octadecanol in core material was found to prevent microcapsules from super-cooling, but the microcapsules were easily conglomerated and their surfaces were extraordinarily rough. Microcapsules with approximately 20 wt.% paraffin in core material were free from super-cooling, and paraffin had no influence on the morphology and dispersibility of microcapsules. (C) 2003 Elsevier B.V. All rights reserved.