Dynamics of supercooled van der Waals liquid under pressure. A dynamic light scattering Tstudy

Dynamics of 1,1-di(p-methoxyphenyl)cyclohexane (BMPC) was studied in a temperature range of 253–313 K and a pressure range of 0.1–180 MPa by means of depolarized dynamic light scattering-photon correlation spectroscopy. The temperature dependence of the mean structural relaxation times measured at constant pressures was analyzed using the VogelFulcher-Tamman (FVT) equation. From the FVT analysis the values of the fragility and the glass transition temperature Tg and T0 as well as their pressure dependence dTg\dP and dT0\dP were obtained and compared with the corresponding quantities obtained for a chemically similar but dynamically different liquid 1,1-di(4-methoxy-5-methylphenyl) cyclohexane (BMMPC), in which two additional intramolecular relaxations were previously reported. The temperature and pressure dependence of the mean structural relaxation times was also analyzed using the Avramov model.