We present a complete set of overlapping pressure-volume-temperature and dielectric relaxation data of the glass forming liquids propylene carbonate, meta-fluoroaniline, and glycerol under pressure up to 700 MPa. In all the samples a glass transition is induced by pressure at constant temperature. We compare the spectral shape of the structural relaxation process in the glass forming liquids with increasing pressure using a simple scaling for the maximum of the dielectric loss. Relaxation times measured at various temperatures and pressures can be scaled on a mastercurve by a single control parameter, the product of temperature and specific volume with a material-dependent exponent. This exponent exhibits the numerical value 4 for van der Waals liquids but is smaller for glass formers with hydrogen bonding.

• Received 20 April 2005

DOI:https://doi.org/10.1103/PhysRevB.72.094204