(560b) Reconfigurable Assemblies of Nanorods Under Changes in Environmental Conditions and Nanorod Shape

Reconfigurable nanostructures represent an exciting new direction for nanomaterials. Applications of reversible transformations between nanostructures can be found in a broad range of advanced technologies including smart materials, electromagnetic sensors, and drug delivery. In this work, we propose two model nanostructures assembled by laterally tethered nanorods that are able to reversibly reconfigure in response to changes in environmental conditions and/or nanorod shape. In the first model, we show that pre-assembled flat bilayer sheets scroll into distinct helical morphologies depending on the solvent selectivity.[1] The local packing of the rods within the sheet and the tether length are shown to be key factors that guide the helix handedness, radius and pitch. When the solvent condition is toggled, either externally or via changes in the building block, the helices transform from one morphology to another. In the second model, we report the formation of two ordered structures, i.e. bilayer sheets and a rectangular grid, assembled by laterally tethered rods with different rod lengths.[2] When the rod segments are elongated or shortened quickly as compared to the system relaxation time, presumably due to certain external stimuli, a reversible transformation between those structures is induced. The kinetic effects due to rod shortening and lengthening are shown to enhance the transformation process over the counterpart self-assembly process from disordered states. These models serve both to inspire the fabrication of laterally tethered nanorods for assembling higher order nanostructures at nanometer scales and as a proof-of-concept for engineering reconfigurable nanomaterials via hierarchical self-assembly. The research was designed and conducted with support by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-02ER46000. The application of shape-matching techniques to structure identification was supported by a grant from the J.S. McDonnell Foundation.

References:

[1] T. D. Nguyen, S. C. Glotzer, Switchable helical structures formed by the hierarchical self-assembly of laterally-tethered nanorods, Small 5, 2092, 2009.

[2] T. D. Nguyen, S. C. Glotzer, Reconfigurable assemblies of shape-changing nanorods, ACS Nano, Published online April 21, 2010.