(315h) Colloidal Templating with Surface-Anisotropic Particles

     Well-ordered, three-dimensional structures, so-called colloidal crystals, are obtained by convective self-assembly of spherical particles. Infiltration of the colloidal structure with a cross-linkable agent and subsequent removal of the colloidal template lead to highly periodic, porous inverse opal structures. Control of the three-dimensional periodicity of such porous structures by means of the colloidal particle size has enormous potential in membrane separation. Additionally, the colloidal particles can also serve as templating agents for catalyst transfer into the membrane structure resulting in catalytic separation membranes. Our work is concerned with the convective assembly of silver-capped polystyrene particles into cylindrical colloidal crystals using microcapillaries and the formation of cylindrical porous polymer membranes with uniform catalyst distributions.

     We will present our data on the convective assembly of anisotropically modified sulfate-terminated polystyrene (PS) microparticles in polymethylmethacrylate (PMMA) micro-capillaries. As a result of capillary forces, cylindrical colloidal crystals with hexagonal-close packing form. Infiltration with a UV curable prepolymer leads to formation of a polymer matrix upon UV curing. The cylindrical porous polymer material with silver caps embedded in the pores forms after exposure to a sequence of organic solvents removing both the PMMA capillary and the PS particles while leaving the silver cap behind. Investigation of the structure and catalyst distribution within the porous membranes is underway using scanning electron microscopy. We will discuss our results in the context of using the porous material for separation of formaldehyde from indoor air.