Dielectric investigations of the molecular dynamics of propanediol in mesoporous silica materials

Broadband dielectric spectroscopy (10−2–1.8×109 Hz) is employed to study the molecular dynamics of the glass-forming hydrogen-bonded liquid propanediol confined to mesoporous M41S silica materials having two different topologies. It is shown that the dynamic glass transition takes place in the mesoporous system (diameter 2.7 nm). With respect to the bulk its relaxation rates are decreased when approaching the calorimetric glass transition. Silanization of the inner surfaces acts as a molecular lubrication and makes the molecular dynamics of the confined liquid comparable to the bulk.