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The effect of confinement by crystals on the α relaxation, observed by dielectric broadband spectroscopy, in isotropic as well as in oriented semicrystalline poly (vinilydene fluoride), is analyzed on the basis of a new thermodynamic model. In both samples, it has been found that the average free-energy barrier, Δ F, for conformational rearrangements is of the same order of the dispersion barrier heights, δ (Δ F), around Δ F, ie, the increase in the barrier height in conformational rearrangement is accompanied by an increase in the heterogeneity of constraining conditions. At a given temperature T, the readjustment free energy is larger in the oriented sample. This fact might be ascribed to either an enhanced effectiveness of confinement in the amorphous region due to the decrease of the amorphous layer thickness in the stacks, or to a change of the mean chain orientation or both. In addition, it is worth noting that in …
American Physical Society
Publication date: 
2 Sep 2010

Amelia Linares, Aurora Nogales, Alejandro Sanz, Tiberio A Ezquerra, Marco Pieruccini

Biblio References: 
Volume: 82 Issue: 3 Pages: 031802
Physical Review E