NIST TRANSFERS NEW POLYMER STRUCTURE ANALYSIS METHOD TO INDUSTRY.

A new method, developed by NIST for determining the molecular architecture of polymers was transferred successfully to a private company. The transfer was facilitated by a recently completed Cooperative Research and Development Agreement (CRADA) in which NIST staff demonstrated their method on materials custom-designed by the private company. The technique was applied to commercial materials to reveal aspects of the chemical structure that were unexpected and impossible to detect by other means.

The new measurement procedure developed at NIST facilitates elucidation of the molecular structure of a class of materials called silsesquioxanes, which have application in a wide array of industries from microelectronics to dental implants. Silsesquioxanes are based on a trifunctional silicon-oxygen monomer having pendant organic side groups. The trifunctional property of the monomer results in condensation polymers with a wide variety of possible three-dimensional configurations. However, industry lacked methods to accurately determine the structure, how the structure develops during manufacture and how the structure influences properties. The analysis challenge was further complicated by a chemical composition that resulted from the use of two different monomers co-polymerized together.

NIST researchers had developed a method using matrix-assisted time-of-flight mass spectrometry (MALDI-TOF-MS), along with autocorrelation analysis of the resulting mass spectra, to determine the topological nature of the molecules as a function of molecular mass. For any molecule having a particular number of silicon atoms, the method can determine the relative number that show a closed topology--polyhedral in shape--versus the number that show an open topology--highly branched in shape. A manuscript that will report on the general method and the results for this example is in preparation.