New method gives insight into nanostructures

A North Carolina State University researcher has created the tools to view the three-dimensional characteristics of internal nanostructures, a development that may lead to greater understanding of nanostructured ‘soft’ materials.

Dr. Richard J. Spontak, associate professor of chemical engineering and materials science and engineering, is conducting research that produces three-dimensional images of complex nanostructures in a variety of multiphase polymer systems.

In collaboration with researchers at the University of California at San Francisco, he is said to have created high-resolution, three-dimensional images that can be measured to extract volumetric and topological metrics.

Until now, researchers have had to be satisfied with highly idealised mathematical models of polymer nanostructures. Thanks to Spontak’s research, they can now have the real thing.

Using electron microscopy techniques developed initially in biology to examine the structure of chromosomes and centrosomes, Spontak applied these methods to polymeric systems. Called ‘electron tomography,’ the technique is similar to the familiar CAT scans performed in medical applications; that is, a three-dimensional volume element is produced through a series of images acquired at different tilt angles. The volume can then be ‘sliced’ into sequential two-dimensional images to allow a viewer to ‘scroll through’ layer by layer.

‘The power behind electron tomography is that we can produce three-dimensional images of complex polymer systems without any a priori assumptions, something that hasn’t been done before,’ said Spontak.

Spontak’s 3-D images are said to have opened a world of possibilities for materials scientists and engineers. According to Spontak, ‘Our greatest contribution is the quantitation of nanostructure in terms of its local and global topology. Using these tools we can create a true picture of the nanostructure as it formed, as well as probe its stability and function. We can characterise nanostructured polymer systems in their natural, unperturbed state without introducing human bias.’

Once scientists understand and can measure more completely the nanostructures of existing polymer molecules, they can use this knowledge to create new kinds of materials and processes. According to Spontak, ‘The main goal of our research has always been to try to design ‘soft’ materials with novel nanostructural characteristics and to relate such characteristics to properties of scientific and technological interest.’

Several technologies are already benefiting from this novel analytical method. Cross-sectional images of multiphase core-shell latex particles help to develop synthesis and stabilisation strategies. Knowing the precise geometry and accessible interfacial area of mesoporous silica derived from nanostructured polymers assists scientists and engineers who intend to use this material in separation processes.

Many of the nanostructured polymer systems investigated so far are industrially useful as hot-melt adhesives, thermoplastic elastomers and physical gels.