Abstract: Amonodispersed latex from styrene(St), methyl methacrylate(MMA) and acrylic acid(AA) was synthesized with the soap free emulsion polymerization, and the formation of colloidal crystal by evaporating the water of the latex was investigated.It has been confirmed that there exist two array manners, i.e., hexagonal and square array, and two packing modes, i.e., hexagonal packing and face-centered cubic packing in the forming process of colloidal crystals.The square array originated from the dislocation of the particle in the hexagonal array, the area of it depends on the temperature in the forming process.At a lower temperature such as at 0℃, relatively large areas of square array were observed in the formed colloidal crystal.

Key words: Colloidal crystal, Hexagonal array, Square array, Hexagonal packing, Face-centered cubic packing