Oriented Composite Mesostructures under Nanoscale Confinement

Rong Kou1, Donghai Wang2, and Yunfeng Lu1. (1) Chemical and Biomolecular Engineering Department, Tulane University, 300 Lindy Boggs Center, Tulane University, New Orleans, LA 70118, (2) Pacific Northwest National Laboratory, Battelle/PNNL, MS:K2-50, Richland, WA 99354

Cooperative assembly of silicate/copolymers results in highly ordered inorganic/organic nanocomposites containing cubic, hexagonal, or lamellar lytropic liquid crystalline mesophases. Subsequent removal of the copolymers creates mesoporous silica with replicated pore structure that often shows non-preferred orientation. Oriented mesostructure is of great interest due to favorable orientations that may provide enhanced device performance. However, fabrications of such oriented and highly ordered mesostructured composite still remain a challenge. In this presentation, we will show shear-induced growth of oriented silicate/copolymer composite nanowires within nanoscale cylindrical alumina pores from nanostructured thin films. Morphology of the oriented composite nanowires were studied using XRD, TEM and SEM. The liquid crystalline silicate/copolymer mesophase is driven into cylindrical alumina pores to form wire-like structure. Shearing force induced the alignment of the composite mesostructure. For example, lamellar silicate/surfactant layers grow along curved pore wall surface, resulting in the formation of oriented concentric lamellar mesophase. The corresponding mesoporous silica wires with oriented hexagonal tubular and concentric lamellar pore channels were also obtained after removal of surfactants. These oriented materials are of interest for membrane separation, templating synthesis, and other applications.