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Broad-band dielectric spectroscopy is employed to study the molecular dynamics of (dielectrically active) glass-forming liquids which are confined to (dielectrically inactive) zeolites and nanoporous glasses. For the H-bond-forming liquid ethylene glycol (EG) embedded in zeolites of different sizes and topologies one observes a sharp transition from a single-molecule dynamics (with an Arrhenius-type temperature dependence) to that of a liquid (with a temperature dependence of the mean relaxation rate following a Vogel-Fulcher-Tammann (VFT) law): while EG in silicalite (showing a single-molecule relaxation) has a coordination number of four, EG in zeolite beta or -5 has a coordination number of five and behaves like a bulk liquid. For the H-bonded liquid propylene glycol confined to (uncoated and silanized) nanopores (pore sizes: 2.5 nm, 5.0 nm and 7.5 nm), a molecular dynamics is observed which is comparable to that of the bulk liquid. Due to surface effects in uncoated nanopores, the relaxation time distribution is broadened on the long-term side and the mean relaxation rate is decreased by about half a decade. This effect can be counterbalanced by lubricating the inner surfaces of the pores. That causes the molecular dynamics of the molecules inside the pores to decouple from the solid walls and the resulting relaxation rate becomes slightly faster compared to that for the bulk liquid. For the `quasi'-van der Waals liquid salol confined to silanized nanopores, the molecular dynamics is completely different to that for the H-bonded systems: over a wide temperature range, the dynamics of the confined system is identical to that of the bulk liquid. But with decreasing temperature, a sharp pore-size-dependent transition is found from a VFT-type to an Arrhenius-type temperature dependence. This reflects the inherent length scale of cooperativity of the dynamic glass transition.

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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.

The synthesis of poly(vinyl ether)s or polyvinylcarbazole under the conditions of constricted geometry can be achieved by means of cationic host-guest polymerisation of the corresponding monomers in the pores of MCM-41 (pore diameter 3.6 nm), MCM-48 (pore diameter 2.4 nm) and in nanoporous glasses (Gelsil with a pore diameter of 5 nm) with bis(4-methoxyphenyl)methyl chloride (BMCC) or triphenylmethyl chloride as the internal surface initiator. The reaction products are new polymer/ MCM-41, polymer/MCM-48 etc., host-guest hybrid materials. The molecular mass of the enclosed polymer and the degree of loading of the host compounds can be adjusted within certain limits. The molecular dynamics were investigated by using broad-band dielectric spectroscopy. Under the conditions of constricted geometry, molecular fluctuation is observed as well as a secondary beta-relaxation, which is hardly affected (in comparison with the free melt) and which corresponds to the relaxation between structural substates (dynamic glass transition). This process is several orders of magnitude faster in its relaxation rate than in the free melt and thus follows a confinement effect. This is already well known in lower molecular weight systems with constricted geometry.