Two-dimensional Raman correlation spectroscopy reveals molecular structural changes during temperature-induced self-healing in polymers based on the Diels-Alder reaction.

The thermally healable polymer P(LMA-co-FMA-co-MIMA) has been studied by temperature-dependent FT-Raman spectroscopy, two-dimensional Raman correlation analysis and density functional theory (DFT) calculations. To the best of our knowledge this study reports for the first time on the investigation of a self-healing polymer by means of two-dimensional correlation techniques. The synchronous correlation spectrum reveals that the spectrally overlapping C[double bond, length as m-dash]C stretching vibrations at 1501, 1575, 1585 and 1600 cm(-1) are perfect marker bands to monitor the healing process which is based on a Diels-Alder reaction of furan and maleimide. The comparison between experimental and calculated Raman spectra as well as their correlation spectra showed a good agreement between experiment and theory. The data presented within this study nicely demonstrate that Raman correlation analysis combined with a band assignment based on DFT calculations presents a powerful tool to study the healing process of self-healing polymers.