화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.104, No.47, 11000-11012, 2000
Diffusive relaxations and vibrational properties of water and H-bonded systems in confined state by neutrons and light scattering: State of the art
A detailed spectroscopic analysis is presented in order to study the reorientational and vibrational dynamics of water and other fundamental H-bonded systems: ethylene glycol (HO-CH2-CH2-OH) and its homologous species, such as ethylene glycol monomethyl ether (CH3O-CH2-CH2-OH) and ethylene glycol dimethyl ether (CH3O-CH2-CH2-OCH3), propylene glycol (HO-CH(CH3)-CH2-OH) and its oligomers, that are confined in a matrix of sol-gel porous glasses with 26 Angstrom interconnected cylindrical pores. The use of different spectroscopic techniques, light scattering (Rayleigh wing and Raman scattering), FT-IR absorption, neutron scattering (incoherent quasi elastic and inelastic neutron scattering, IQENS and IINS, respectively) allow the marking of different dynamical parameters, with different probes being used to investigate H-bonded systems. The clear influence of the confinement on the mobility of the studied liquids, with a dramatic frozen-in observed effect respect to the bulk state, is evidenced and compared with literature results. Furthermore, a surface-liquid potential well induces strong modifications of the local symmetry of the vibrational groups (e.g., the active OH stretching groups) involved in the interaction, giving rise to anharmonic effects (red shift, band enlargement) that depend on the nature of the surface (hydrophobic or hydrophilic) and on the nature of guest liquids (wetting or nonwetting).