Poly(ethylene-2,5-furandicarboxylate) (PEF) is a new alipharomatic polyester that can be prepared from monomers derived from renewable resources like furfural and hydroxymethylfurfural. For this reason it has gained high interest recently. In the present work it was synthesized from the dimethylester of 2,5-furandicarboxylic acid and ethylene glycol by applying the two-stage melt polycondensation method. The thermal behavior of PEF was studied in comparison to its terephthalate and naphthalate homologues poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN), which were also synthesized following the same procedure. The equilibrium melting point of PEF was found to be 265 °C while the heat of fusion for the pure crystalline PEF was estimated to be about 137 J g(-1). The crystallization kinetics was analyzed using various models. PET showed faster crystallization rates than PEN and this in turn showed faster crystallization than PEF, under both isothermal and non-isothermal conditions. The spherulitic morphology of PEF during isothermal crystallization was investigated by polarized light microscopy (PLM). A large nucleation density and a small spherulite size were observed for PEF even at low supercoolings, in contrast to PET or PEN. Thermogravimetric analysis indicated that PEF is thermally stable up to 325 °C and the temperature for the maximum degradation rate was 438 °C. These values were a little lower than those for PET or PEN.

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In this work we report the observation of two different crystalline patterns of poly­(ethylene furanoate) (PEF), corresponding to bulk and solvent induced crystallization. The crystal form generated by bulk crystallization is the α-form, while that observed after solvent crystallization is the β-form. Crystal transition upon heating was not evidenced. However, in the case of bulk crystallization, the defective (α′) crystal structure generated under large supercoolings (at temperatures well below 180 °C), was reorganized to a more perfect structure of the same form (α) when heated above 190 °C. Three new peaks at 13.8°, 18.1°, and 26.7° were recorded after annealing at such elevated temperatures. Moreover, the melting temperature of PEF steadily increased, with increasing temperature of isothermal crystallization. Temperature modulated differential scanning calorimetry studies showed enhanced recrystallization upon heating for the samples crystallized under large supercoolings. However, for samples crystallized at 170 °C or above, two nonreversing melting peaks were observed and these were attributed to the melting of crystals of different stabilities. Recrystallization was evidenced after these melting peaks. For samples crystallized at 200 °C, only a weak recrystallization peak was recorded, after the double nonreversing melting. No indication for recrystallization/reorganization was observed for the solvent-crystallized samples. Finally, it was realized that fresh PEF samples always crystallized faster than those that suffered repeating melting. This was also observed for other furanoates, but is in contrast to what is observed for their terephthalate or napthalate counterparts.

In this study, biobased furan dicarboxylate polyesters have been prepared using 2,5‐furandicarboxylic acid (FDCA) and diols with high number of methylene groups (long‐chain diols), namely, 8, 9, 10, and 12. Because of the high boiling points of these diols, a modified procedure of the well‐known melt polycondensation was applied in this work. According to this, the dimethyl ester of FDCA (DMFD) reacted in the first transesterification stage with the corresponding diols forming bis‐hydroxy‐alkylene furan dicarboxylates (BHFD). In the second stage, the BHFD reacted with DMFD again at temperatures of 150–170 °C (for 4–5 h), and in the final stage, the temperature was raised to 210–230 °C (vacuum was applied for 2–3 h). The molecular weight of the polyesters and the content of oligomers, as was verified by gel permeation chromatography analysis, depend on the polycondensation time and temperature. The chemical structure of the polyesters was verified from 1H NMR spectroscopy. All the polymers were found to be semicrystalline, with melting temperatures from 69 to 140 °C depending on the diol used. In addition, the mechanical properties also varied with the type of diol. The higher values were observed for poly(octylene 2,5‐furanoate), whereas the lowest values were observed for poly(dodecylene 2,5‐furanoate) with the higher number of methylene groups in its repeating unit. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2617–2632

Poly(dodecylene 2,5-furanoate) (PDoF) is a novel alipharomatic polyester which was prepared by combining a long chain glycol as the monomer (1,12-dodecamethylene glycol) and 2,5-furan dicarboxylic acid (FDCA), which can be derived from biomass. A variation of the well-known two-step polycondensation method was applied for the preparation of PDoF. The glass transition temperature of this polyester, which was recorded by using fast scanning calorimetry (FSC) is observed at −5 °C. The melting temperature is about 111 °C while the equilibrium melting temperature was extrapolated through Hoffman−Week plots to 127.3 ± 0.2 °C. New insights in the complex melting behavior were obtained by employing conventional and temperature modulated calorimetry. The crystallization kinetics in isothermal and nonisothermal modes were investigated by means of Avrami and Lauritzen−Hoffman models and model-free kinetics. The thermal stability of PDoF was reduced in comparison with previously studied furanoates, as a result of the flexible macromolecular chains of the material, while the nucleation density was high and the spherulitic size was small.

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