Dielectric studies of the glass transition in porous media

Dynamic processes in liquid propylene glycol and two of its oligomers inside the 100 pores of controlled porous glasses have been investigated as a function of temperature by dielectric spectroscopy. We find that geometrical restriction results in retardation and broadening of the inherent relaxation. This retardation is most pronounced for the monomer liquid and gives rise to an increase in the glass transition temperature by TG=+4.5 K. We also observe a second slower relaxation process for all liquids, ascribed to the hindered dynamics of molecules affected by the surface.