Broadband Dielectric Spectroscopy Study of Biobased Poly(alkylene 2,5-furanoate)s’ Molecular Dynamics

Abstract

Poly(2,5-alkylene furanoate)s are bio-based, smart, and innovative polymers that are considered the most promising materials to replace oil-based plastics. These polymers can be synthesized using ecofriendly approaches, starting from renewable sources, and result into final products with properties comparable and even better than those presented by their terephthalic counterparts. In this work, we present the molecular dynamics of four 100% bio-based poly(alkylene 2,5-furanoate)s, using broadband dielectric spectroscopy measurements that covered a wide temperature and frequency range. We unveiled complex local relaxations, characterized by the simultaneous presence of two components, which were dependent on thermal treatment. The segmental relaxation showed relaxation times and strengths depending on the glycolic subunit length, which were furthermore confirmed by high-frequency experiments in the molten region of the polymers. Our results allowed determining structure–property relations that are able to provide further understanding about the excellent barrier properties of poly(alkylene 2,5-furanoate)s. In addition, we provide results of high industrial interest during polymer processing for possible industrial applications of poly(alkylene furanoate)s.

Evidence of Nanostructure Development from the Molecular Dynamics of Poly(pentamethylene 2,5-furanoate)

“…This could be the reason why in previous reports this polymer has been considered as fully amorphous in the bulk. [23][24]56 Crystallinity values (Xc), calculated from XRD scans, were 3 ± 1 %, 7 ± 2 % and 17 ± 2 % for samples with storage times of 4, 10 and 12 months, respectively. Concerning XRD results, we highlight that in the article by Guidotti and collaborators, the authors detected a sharp and intense reflection at = 1.26 Å -1 for an amorphous PPeF sample.…”

“…The faster component was called 1 , and the slower one 2 , in line with our previous report on poly(alkylene 2,5-furanoate)s' molecular dynamics. 56,58 Lines in Figure 4a are representative fitting curves. In Figure 5, we show the temperature dependence of the resulting fitting parameters, for all three samples.…”

“…23,25 Specifically, the different number of methylene groups has a direct effect on the chain mobility and crystallizing capability. 23,[55][56] These characteristics allow to obtain from amorphous to semicrystalline polymers, which at room temperature can be in the glassy or in the rubbery state. According to these features, a different microstructure can develop, having a direct effect on the macroscopic properties.…”

“…24 PPeF is characterized by a glass transition temperature below room temperature and shows crystallization kinetics so slow that, under normal conditions, it can be considered completely amorphous. 24,[55][56] Despite these characteristics, PPeF can be processed as films and, very surprisingly, it exhibits an elastic mechanical response at room temperature, as well as exceptional barrier properties. 24,55 This behavior has been explained on the basis of particular inter-chain interactions, 24 also proposed for the other polymers of the family.…”

“…Our results provide new insights on the study of this polymer and differentiate 4 from previous publications, where the material was considered as fully amorphous 23 and with physical properties independent from thermal history. 56…”