Raman spectroscopy and molecular bases of elasticity: SEBS-graphite composites

For polymer-based (nano)composites, the strain/stress induced by reinforcing agents within the polymer may be identified and quantified at molecular level by Raman spectroscopy. The manuscript focuses on correlations between mechanical properties of composites and their Raman spectra, with emphasis on the displacements of the position(s) of Raman lines due to local strains/stress. Investigations on polystyrene-(ethylene-co-butylene)-styrene block copolymers filled with various amounts of graphite are reported. The modifications of Raman's parameters (line intensity, position, and width) upon the loading with graphite are analyzed. Raman revealed a strong dampening of molecular vibrations within the polymer, upon the loading with graphite, indicating a good mechanical coupling between the polymer and the reinforcing agent. Significant differences between Raman spectra obtained with green and red lasers, were reported; Raman spectra obtained with red laser are more sensitive to motions occurring within the polymer while the spectra obtained using green laser are more sensitive to graphite.