To advance materials science, researchers at NIST have developed a new way to measure the 3D orientation of molecules within a material made of components called polymers. In this illustration, the pinlike forms represent polymer chains, with the color indicating average angle off the vertical plane and the size of the pinhead representing the distribution of orientations around that average. The image in the background shows the raw data, which is produced by a method known as broadband coherent anti-Stokes Raman scattering, or BCARS.
Credit: Y.J. Lee/NIST
In some materials, the molecules line up in a regular, repeating pattern. In others, they all point in random directions. But in many advanced materials used in medicine, computer chip manufacturing and other industries, the molecules arrange themselves in complex patterns that dictate the material’s properties.
Scientists haven’t had good ways to measure molecular orientation in three dimensions at a microscopic scale, leaving them in the dark about why some materials behave the way they do. Now, researchers at the National Institute of Standards and Technology (NIST) have measured the 3D orientation of the molecular building blocks of plastics, called polymers, observing details as small as 400 nanometers, or billionths of a meter, in size.
The measurements, described in the Journal of the American Chemical Society, show polymer chains twisting and undulating in complex and unexpected ways. The new measurements were made using a souped-up version of a technique called broadband coherent anti-Stokes Raman scattering, or BCARS.
BCARS works by shining laser beams at a material, causing its molecules to vibrate and emit their own light in response. This technique, developed about a decade ago at NIST, is used to ..
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