The small-angle X-ray scattering (SAXS) and the low-frequency Raman scatter
ing (LFRS) of pure and plasticized poly(methyl methacrylate) (PMMA) samples
are compared. A correlation peak in SAXS appears in plasticized PMMA at ab
out 0.15 Angstrom(-1), which does not exist in pure PMMA. An increase of th
e boson peak intensity with the amount of plasticizer is observed. These ob
servations allow to sustain the relation between the boson peak and inhomog
eneous nanostructure in glasses.