Vibrational properties of a reactive mixture investigated during a chemical vitrification process

Raman and Brillouin light scattering measurements were performed to follow the modification of the vibrational properties of a reactive epoxy-amine mixture during isothermal polymerization. We analyze the variations of the vibrational density of states while the system changes from liquid to glass upon increasing the number of covalent bonds among the constituent molecules. The spectral shape of the boson peak follows a precise and universal scaling law. Surprisingly, bond-induced modifications of the structure do not affect this master curve. Moreover the Brillouin scattering results here reported for a curing epoxy system provide evidence for the validity of a Cauchy-like relation.