Green polymeric materials: On the dynamic homogeneity and miscibility of furan-based polyester blends

Polyesters from 2,5-furandicarboxylic acid are considered as biobased alternatives to their terephthalate counterparts. This work is focused on polymer blends comprised of furan-based polyesters differing by one or two methylene groups in their repeat units. Blends of Poly(ethylene 2,5-furandicarboxylate) (PEF) and poly (propylene 2,5-furandicarboxylate) (PPF) displayed a single composition-dependent glass temperature (T-g). Dielectric spectroscopy results revealed dynamically homogeneous mixtures when the backbones differ by a single methylene unit and dynamically heterogeneous mixtures when they differ by two methylene units. The most interesting finding was the single segmental dynamics in the PEF-PPF and poly(butylene furanoate)-poly (propylene furanoate) (PBF-PPF) blends. For comparison, homologous terephthalate blends were also investigated. Finally, reactive blending was applied in PEF-PBF blends and enhanced compatibility was achieved even after short times due to transesterification reactions at elevated temperatures. With increasing duration of melt-mixing the thermodynamic miscibility between PEF and PBF increased and ultimately a random copolymer was obtained.