The effect of pressure on the glass transition temperature of a variety of molecular liquids both hydrogen bonded and non-hydrogen bonded, and their solutions has been investigated. It is found generally that the more extensive the hydrogen bonding in the liquid the smaller is the effect of pressure on Tg. This observation applies also to a binary mixture, in which dTg/dP is found to change linearly between the end member values. The effect of pressure on the glasslike transition in the cyclohexanol plastic crystal phase is as expected for a liquid alcohol. For the lubricant 5P4E, the data are in accord with predictions based on high-pressure light scattering data. The results are interpreted by using the second Davies-Jones relation, dTg/dP = VT(Δα/ΔCp). Some evidence suggesting that the excess entropy frozen in at the glass transition is not quite independent of pressure as often supposed is presented.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry