Effect of physical aging on nano- and macroscopic properties of poly(methyl methacrylate) glass

Physical aging of amorphous poly(methyl methacrylate) has been studied by low frequency Raman scattering, broad-band dielectric spectroscopy, low frequency high resolution mechanical spectroscopy and differential scanning calorimetry. The material was subjected to different thermal histories by isothermal aging. A consistent relationship between the changes caused by the physical aging in nanostructure and molecular dynamics has been found. The aging makes the structure more homogeneous at a scale of few nanometers, bringing it to a structural state of lower energy. These structural changes affect mainly the a-relaxation, however, sorne increase in the relaxation strength as well as an increase in the activation energy of the beta-relaxation is also observed. (c) 2006 Elsevier Ltd. All rights reserved.