Scaling out the density dependence of the $α$ relaxation in glassforming polymers

Abstract

We show that the density and temperature dependences of the $α$-relaxation time of several glassforming polymers can be described through a single scaling variable $X=e(ρ)/T$, where $e(ρ)$ is well fitted by a power law $ρ^x$, $x$ being a species-specific parameter. This implies that ``fragility'' is an intrinsic, density-independent property of a glassformer characterizing its super-Arrhenius slowing down of relaxations, and it leads us to propose a modification of the celebrated Angell plot.

8 pages, 4 figures