Well-Defined Hierarchical Templates for Multimodal Porous Material Fabrication

Hierarchical templates with raspberry-like and strawberry-like features were prepared by synthetically joining appropriately functionalized commercially available polystyrene (PS) latex spheres together. Two different coupling reactions were used to form the hierarchical templates: carbodiimideassisted coupling of COOH groups with NH(2) groups and base-assisted coupling of epoxy groups with NH(2) groups. Since the templates are made by chemically bonding PS spheres together, both the core and satellite spheres can be different sizes. In this work, hierarchical spheres with core/satellite diameters of 1500/110 nm, 450/80 nm, 340/29 nm, and 1200/29 nm were made. The spheres were isolated and then used as hierarchical templates to prepare porous materials with well-defined architecture. Multimodal porous silica and bimodal macroporous gold electrodes were fabricated using the 1500/110 nm hierarchical template. Because the templates were constructed of only one material, polystyrene, they were easily removed from the host material to yield the macroporous material with pores of well-defined sizes that corresponded to the size of the template. It is envisioned that these hierarchical porous supports will be useful in chemical sensing and other applications that require large open pores to minimize diffusion restraints and smaller pores to increase surface area.