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R&D Profile: Nanoparticle Arrays Templated in Thermoreversible Micelle Crystals, D. Pozzo, University of Washington, US

The design of materials with tailored properties and function requires control over structure at the nanometer scale. Engineering applications also require that this control is carried out using parallel self-assembly processes that occur simultaneously in large numbers and reasonable timescales.

Research Overview and Updates Courtesy of Dr. Danilo Pozzo, University of Washington, US

The design of materials with tailored properties and function requires control over structure at the nanometer scale. Engineering applications also require that this control is carried out using parallel self-assembly processes that occur simultaneously in large numbers and reasonable timescales. Block copolymers form highly organized structures when they are dissolved in solvents that are selective to one of the polymer blocks. A general method to template nanoparticle arrays using thermoreversible block-copolymer mesophases has been recently presented.[1-3] We show that shear orientation can be used to generate crystalline nanocomposite structures with long range organization over macroscopic length scales (centimeters). The resulting shear-aligned nanocomposite is a single macro-domain in which the block-copolymer template and the dispersed nanoparticles share the same lattice and orientation. Small angle neutron scattering (SANS) experiments show that shear alignment is possible in mesophases of cubic micelle crystals as well as in close-packed arrays of cylindrical micelles. We find that the rate of shear, the temperature history, and the relative size and concentration of nanoparticles in the composites are all critical in determining the extent of organization. This general and scalable method represents a simple but significant improvement in our ability to manipulate materials at the nanometer length scales.

SANS profile micelle crystal and templated schematic representation of nanocomposite

Figure: SANS profile for a shear-aligned micelle crystal template and the schematic representation of a templated nanocomposite.

The Walker group at Carnegie Mellon University continues to pursue a fundamental understanding of block copolymer assisted nanoparticle organization. Their current work focuses on the relationship between shear and structure in these composite materials, the further extension to cylindrical and other symmetries and the nature of the dispersed phase in the templated material, particularly the dynamics and local environment.

Meanwhile, the Pozzo group at the University of Washington is investigating the application of self-organized polymeric matrices to improve the speed and resolution of analytical proteomic separations. The goal of this research is to determine the intricate relationship between the specific geometry and nanostructure of the matrix, the mode of transport of the polyelectrolytes (e.g. reptation) and the overall efficiency of the electrophoretic separation (speed and peak resolution). In addition, the group is also extending the principles of guided self-assembly to the scale-up of nanomaterial synthesis. This is a critical bottleneck for the development of economical applications in nanotechnology. Currently, the group is developing scaleable methods that add directionality to specific interparticle bonds. This is essential for the intelligent design and parallel fabrication of multi-particle complexes (nanoassemblies).

  1. Pozzo DC, Walker LM: Three-dimensional nanoparticle arrays templated by self-assembled block-copolymer gels. Macromolecular Symposia 2005, 227:203-210.
  2. Pozzo DC, Walker LM: Shear orientation of nanoparticle arrays templated in a thermoreversible block copolymer micellar crystal. Macromolecules 2007, 40:5801-5811.
  3. Pozzo DC, Walker LM: Small-angle neutron scattering of silica nanoparticles templated in PEO-PPO-PEO cubic crystals. Colloids and Surfaces a-Physicochemical and Engineering Aspects 2007, 294:117-129.
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