Temperature-induced polymorphism in bio-based poly(propylene 2,5-furandicarboxylate)

Highlights: • Melt crystallized PPF exhibits three different crystalline forms (α′, α and β). • α′- and α-crystals grow mainly at T_c < 140 °C. • β-crystals grow at T_c ≥ 140 °C. • Depending on the crystallization temperature, the different crystalline forms can coexist. • The defective α′-crystals transform into the more perfect α-form at about 160 °C. -- Abstract: For the academic and industrial research that aims at substituting plastics derived from fossil feedstock with bio-based alternatives, the furandicarboxylate-based polyesters are a very promising family of materials, because they exhibit enhanced properties for advanced applications. In order to lay the foundation for the comprehension of the relationships between crystallization process and final properties for these materials, a detailed investigation on the crystal structure of poly(propylene 2,5-furandicarboxylate) (PPF) has been performed. The study has revealed that PPF exhibits polymorphism when crystallized from the melt. Three forms have been identified, as well as a crystal transformation from a defective to a more perfect crystal structure upon heating. The different crystal modifications coexist, depending on the crystallization temperature. The relationship between polymorphism and melting behavior has been investigated, and the peaks that constitute the multiple melting endotherm assigned. This is the first case of polymorphism involving three crystal forms that is observed for bulk crystallized furandicarboxylates-based polyesters.