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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.

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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.

16Poly(2,2-dimethyl-1,3-propylene furanoate) (PDMPF), an interesting sustainable biobased 17 polyester based on 2,5-furan dicarboxylic acid (FDCA), was synthesized by applying the 18 two-stage melt polycondensation method. The polyester exhibited a melting temperature of 19 T m =198 o C and a glass transition temperature of T g =68 o C. Multiple melting was observed for 20 the samples crystallized isothermally at temperatures ranging from 160 to 175 o C. Extensive 21 recrystallization was evidenced by modulated temperature differential scanning calorimetry 22 (MDSC) during heating. The equilibrium melting temperature was found equal to T m o =222 23 o C and the enthalpy of fusion of the pure crystalline polymer was ∆Η f =133 J/g. The 24 crystallization rates were analyzed according to the secondary nucleation theory and a 25 relatively large nucleation constant K g was obtained, representing the rigidity of the 26 macromolecular chains. Large spherulites were observed during isothermal crystallizations 27 tests with the aid of polarized light optical microscopy (PLOM). The polyester showed 28 significant stability during the thermal degradation tests. Finally, the degradation mechanism 29was investigated by employing a pyrolizer-gas chromatography-mass spectroscopy (Py-GC-30 MS) system.

Poly(ethylene furanoate) (PEF) is a fully bio-based polyester with unique gas barrier properties, considered an alternative to poly(ethylene terephthalate) (PET) in food packaging applications. However, it is not biodegradable. For this reason copolymerization with the aliphatic succinic acid monomer, was followed. The respective poly(ethylene furanoate-co-ethylene succinate) (PEFSu) copolymers were prepared via melt polycondensation from 2,5-dimethylfuran-dicarboxylate, succinic acid and ethylene glycol at different ratios.1 HNMR spectroscopy showed the copolymers are random. The crystallization and melting of the copolymers were thoroughly evaluated. Isodimorphic cocrystallization was concluded from both the 2 WAXD patterns and the minimum in the plots of melting temperature versus composition. The pseudo-eutectic melting point corresponded to an ethylene succinate content of about 30 mol%. The enzymatic hydrolysis tests using of Rhizopus delemarand Pseudomonas Cepacia lipase, revealed that the copolymers with up to 50 mol% ES units show measurable weight loss rates. For higher ES content, the copolymers showed fast hydrolysis.

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