Among all the emergent biobased polymers,
poly(ethylene 2,5-furandicarboxylate)
(2,5-PEF) seems to be particularly interesting for packaging applications.
This work is focused on the investigation of the relaxation dynamics
and the macromolecular mobility in totally amorphous 2,5-PEF as well
as in the less studied poly(ethylene 2,4-furandicarboxylate) (2,4-PEF).
Both biopolymers were investigated by differential scanning calorimetry
and dielectric relaxation spectroscopy in a large range of temperatures
and frequencies. The main parameters describing the relaxation dynamics
and the molecular mobility in 2,5-PEF and 2,4-PEF, such as the glass
transition temperature, the temperature dependence of the α
and β relaxation times, the fragility index, and the apparent
activation energy of the secondary relaxation, were determined and
discussed. 2,5-PEF showed a higher value of the dielectric strength
as compared to 2,4-PEF and other well-known polyesters, such as poly(ethylene
terephthalate), which was confirmed by molecular dynamics simulations.
According to the Angell’s classification of glass-forming liquids,
amorphous PEFs behave as stronger glass-formers in comparison with
other polyesters, which may be correlated to the packing efficiency
of the macromolecular chains and therefore to the free volume and
the barrier properties.