In some substances, the molecules align in a predictable, recurring pattern. They all point in different directions in some of them. However, the molecules arrange themselves in intricate patterns that determine the qualities of many high-tech materials used in producing computer chips, creating medical devices, and other industries.
The inability of scientists to accurately determine molecular orientation in three dimensions at the microscopic level has left them unsure of the causes of certain materials’ peculiar behaviors.
In order to assess the 3D orientation of polymers, the chemical building blocks of plastics, researchers at the National Institute of Standards and Technology (NIST) had to look at details as fine as 400 nanometers, or billionths of a meter, in size.
The data, which are detailed in the Journal of the American Chemical Society, demonstrate the complicated and surprising twisting and undulating of polymer chains. A beefed-up variation of a method known as broadband coherent anti-Stokes Raman scattering, or BCARS, was used to make the new measurements.
By directing laser beams to a material, BCARS causes its molecules to vibrate and release their own light. This method, created around ten years ago at NIST, is used to determine the composition of a material.
Young Jong Lee, a research chemist at NIST, introduced a technology to regulate the polarization of the laser light and new mathematical techniques to analyze the BCARS signal to detect molecular orientation.
The novel method specifically evaluates the dispersion of orientations around the average orientation of the polymer chains within 400-nanometer areas. These observations will enable researchers to pinpoint the patterns of molecule orientation that result in the desired mechanical, optical, and electrical properties.
“Understanding that structure/function relationship can really speed up the discovery process,” Lee said.
This will aid in the material optimization process for medical devices like replacement knees and vascular stents. How successfully those devices bond with muscle, bone, and other tissues depends in part on the orientation of the molecules on their surface.
Additionally, it can aid in additive manufacturing, a process that is revolutionizing electronics, automotive, aerospace, and other industries. In additive manufacturing, objects are constructed by 3D printing them layer by layer. Polymers are frequently used in 3D printing, and scientists are always looking for new ones with improved strength, flexibility, heat resistance, and other qualities.
The polymer-based ultrathin films used in semiconductor production may potentially be optimized using the novel measurement method. The molecule orientations in those films become more significant as Moore’s law predicts that components within computer chips will get smaller and smaller.
