Controlled photooxidation of polymeric colloidal crystals for surface patterns tuning

Most polymers are not inherently stable to light, but this weakness of polymers can be exploited in a positive way. In this paper, we report a simple approach to modifying the surface patterns produced by polystyrene (PS) colloidal crystals by taking advantage of their instabilities under UV illumination. Colloidal crystals grown from PS colloidal suspension were prepared and exposed to the UV light. As a consequence of photochemical reactions, UV irradiation induced morphological changes in the film surface including changes in size and shape of PS particles. Specifically, the particle surface areas illuminated by the UV light in the colloidal crystal films could be controlled by tilting the films, to yield unique surface patterns, including complex and delicate surface patterns. The proposed approach provides a simple route to fabricating colloidal crystal masks with unique structures and without the need for special equipment.