Relaxation dynamics of H-bonded liquids confined in porous silica gels by Rayleigh wing spectroscopy

Reorientational dynamics of neat liquid propylene glycol molecules is compared with that of confined molecules in 25 and 75 Å pores of a sol-gel porous glass by means of depolarized light-scattering spectroscopy. The experimental spectra, performed as a function of temperature, show unambiguously the slowing down of the collective reorientational processes triggered by the confinement effects. Such results confirm the main role played by the strong dipolar interactions on the dynamics of hydrogen-bonded liquids diffusing within nanoscopic spherical pores.