Stress-induced modification of the boson peak scaling behavior

The scaling behavior of the so-called boson peak in glass-formers and its relation to the elastic properties of the system remains a source of controversy. Here, the boson peak in a binary reactive mixture is measured by Raman scattering (i) on cooling the unreacted mixture well below its glass transition temperature and (ii) after quenching to very low temperature the mixture at different times during isothermal polymerization. These different paths to the glassy phase are able to generate glasses with different amounts of residual stresses, as evidenced by the departure of the elastic moduli from a Cauchy-like relationship. We find that the scaling behavior of the boson peak with the properties of the elastic medium --- as measured by the Debye frequency --- holds for states in which the system is able to release internal stress and breaks down in the presence of residual stresses. These findings provide new insight into the boson peak behavior and are able to reconcile the apparently conflicting results presented in literature.