Scaling behavior of the Raman intensity and heterogeneous elasticity during the chemical vitrification of an epoxy resin

Abstract

The density of vibrational states of amorphous materials deviates from that expected from the Debye model, giving rise to a characteristic excess of states known as boson peak (BP). Despite the long-standing interest in this characteristic feature, its origin and behavior remain a source of controversy, in particular its scaling behavior and its relation to the elastic properties of the material. In this regard, the theory of elastic heterogeneity, based on the notion that the structural disorder induces spatially fluctuating local elastic moduli, offers an interesting reading key for the BP behavior. In this paper we consider the evolution of the Raman signal in the BP region, during the isothermal vitrification process of an epoxy resin induced by the progressive polymerization of the molecules in the system, and provide a critical discussion of the observed scaling behavior in the framework of the theory of heterogeneous elasticity.