Near-Edge X-ray Absorption Fine Structure Spectroscopy of
MDI and TDI Polyurethane Polymers

Stephen G. Urquhart ,† Archie P. Smith, † Harald W. Ade, † Adam P. Hitchcock, ‡
Edward G. Rightor, § and Werner Lidy |

†Department of Physics, North Carolina State University, Raleigh, North Carolina, 27695-8202,
‡Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, L8S 4M1, Canada,
 §Dow Chemical USA, Midland, Michigan, 48667
 |Dow Chemical USA, Freeport, Texas, 77541
Received: January 5, 1999; In Final Form: March 31, 1999

The sensitivity of near-edge X-ray absorption fine structure (NEXAFS) to differences in key chemical
components of polyurethane polymers is presented. Carbon 1s NEXAFS spectra of polyurethane polymers
made from 4,4-methylene di-p-phenylene isocyanate (MDI) and toluene diisocyanate (TDI) isocyanate
monomers illustrate that there is an unambiguous spectroscopic fingerprint for distinguishing between MDI-based
and TDI-based polyurethane polymers. NEXAFS spectra of MDI and TDI polyurea and polyurethane
models show that the urea and carbamate (urethane) linkages in these polymers can be distinguished. The
NEXAFS spectroscopy of the polyether component of these polymers is discussed, and the differences between
the spectra of MDI and TDI polyurethanes synthesized with polyether polyols of different molecular
composition and different molecular weight are presented. These polymer spectra reported herein provide
appropriate model spectra to represent the pure components for quantitative microanalysis.