Broadband dielectric spectroscopy of water confined in MCM-41 molecular sieve materials—low-temperature freezing phenomena

Dielectric properties of water adsorbed in pure siliceous and aluminium containing mesoporous MCM-41 materials have been investigated in the frequency range from 20 Hz to 1 MHz. The dielectric spectra revealed three dispersion regions, liquid-like free water in the centre of the mesopores, an intermediate water layer with reduced mobility, and an interfacial water layer at the inner surface of the mesopores. The analysis of the relaxation time distribution by means of a double-well potential indicates a strong dependence of the barrier height of reorienting water molecules dipoles in the interfacial layer on the Si/Al ratio in the framework.