Pressure and Temperature Dependence of the Dilute Solution Segmental Dynamics of Anthracene-Labeled Polyisoprene

The local segmental dynamics of anthracene-labeled cis-1,4-polyisoprene in dilute solution have been studied as a function of temperature (298−323 K) and pressure (0.1−150 MPa) in several solvents (dioctyl phthalate, n-dodecane, squalane, and toluene). This range of temperature and pressure afforded a viscosity range of 0.55−494 mPa·s. Previous studies of cis-1,4-polyisoprene as a function of temperature at ambient pressure have revealed that these motions scale as a fractional power of the solvent viscosity, η, thereby violating Kramers' theory which predicts τ c ∼ η. Findings reveal quantitatively similar behavior is observed when the solvent viscosity is varied by pressure at fixed temperatures.