EXPRESS: Two-Dimensional Correlation Spectroscopy (2D-COS) Analysis of Near-Infrared (NIR) Spectra of Hydrogen-Bonded Elastomer Under Mechanical Stress

We investigated the deformation mechanism of a phenyl urazole-functionalized polybutadiene elastomer crosslinked via hydrogen bonds (H-bonds) using rheo-optical near-infrared (NIR) spectroscopy and two-dimensional correlation spectroscopy (2D-COS). The elastomer sample experienced tensile deformation while being probed by a high-speed NIR spectrometer equipped with an acousto-optic tunable filter (AOTF). The main feature of the NIR spectra of the elastomer sample is a change in the intensity of a broad peak consisting of multiple sub-peaks each reflecting different states of H-bonding. The NIR spectra was then subjected to 2D-COS analysis to resolve overlapping H-bonding bands, enabling their sequential structural evolution to be determined. Asynchronous analysis suggested that the deformation of H-bonds in the soft matrix likely precedes the disruption of rigid aggregates. This study demonstrates the utility of 2D-COS-assisted rheo-optical NIR spectroscopy in revealing the behavior of H-bonds in elastomers under stress.