Abstract
We present detailed studies of variation in segmental and chain dynamics of polyisoprene under
pressure. Samples with two molecular weights (MW), 2.4 and 25 kg/mol (below and above entanglement), were investigated. Dielectric spectroscopy measurements at isobaric and isothermal conditions exhibit clear differences in temperature and pressure dependencies of chain and segmental relaxation times. Moreover, application of pressure increases time separation between the segmental and normal (chain) modes at the isochronic conditions. This increase can be explained by an effective increase in number of Rouse segments under compression at the same segmental relaxation time. Our analysis also reveals that the thermodynamic scaling of the relaxation times (log τ vs TVγ, V is volume) does not work well simultaneously for both processes.
