Molecular dynamics of novel poly(pentamethylene 2,5- furanoate): Exploring a complete landscape of molecular dynamics and finding unexpected results

Resumen del trabajo presentado a la 10th Conference on Broadband Dielectric Spectroscopy and its Applications (BDS) celebrada en Bruselas (Belgica) del 26 al 31 de agosto de 2018.In the last decade, there has been an increased interest toward the development and application of bioplastics, to contribute to the sustainable economy and to help reducing environmental problems. Among bioplastics, particular attention is devoted to biobased polymers synthesized from 2,5-furan dicarboxylic acid (2,5-FDCA). Furan-based polymers with an even number of methylene units are able to crystallize, leading to the formation of a phase-separated material, i.e. a semicrystalline polymer. This is the case of poly(ethylene 2,5-furanoate) (PEF), poly(butylene 2,5-furanoate) (PBF), and poly(hexamethylene 2,5-furanoate) (PHF), where broadband dielectric spectroscopy (BDS) studies have been carried out by different groups and changes in both local and segmental relaxations were observed as the system crystallized. In this work, we explore the molecular dynamics of poly(pentamethylene 2,5-furanoate) (PPeF), a furan-based polyester with an odd number of methylene groups. Surprisingly, while differential scanning calorimetry and wide-angle X-ray scattering results showed no evidences of PPeF crystallization, BDS experiments showed changes in both local and segmental dynamics. By BDS, we observed an overall dependence of the PPeF dynamics with thermal history, characterized by the dissapearance of one component describing the local relaxation, and the slow down of the segmental relaxation without significant changes in its shape. These BDS results in PPeF suggest the development of unusual structural features in this material, different from those of a semicrystalline state, as a “frustrated” crystallization or even the possible formation of a mesophase.Peer reviewe