High Pressure Local Dynamics of Bulk Polymers

Time-resolved optical spectroscopy has been used to monitor the local segmental dynamics of bulk cis-1,4-polyisoprene (PI) and bulk cis-1,4-polybutadiene (PB) as a function of pressure at various temperatures. Reported activation volumes are observed to be independent of pressure but dependent on temperature with the constant pressure activation energies being independent of temperature but significantly dependent on pressure. Average dT/dP values of 0.20 K/MPa for PI and 0.15 K/MPa for PB are determined from the high pressure data in good agreement with values determined from bulk viscoelasticity measurements. Furthermore, ratios for both polymers of the constant volume activation energy to the constant pressure activation energy are greater than 0.5.