Synthesis and structure – property relationship of biobased poly(butylene 2,5-furanoate) – block – (dimerized fatty acid) copolymers

A series of poly(butylene 2,5-furanoate) – block – (dimerized fatty acid) (PBF-b-FAD) copolymers were successfully synthesized from 2,5-furandicarboxylic acid (FDCA), 1,4-butanediol (1,4-BD), and dimerized fatty acid diol (FADD) via a polycondensation in melt under the relatively mild process conditions and a reasonable excess of diol. The copolymers with different PBF to FAD segment ratio were characterized in regard of their chemical composition, microstructure, thermal transitions and stability as well as the mechanical performance. Some results were also discussed in relation to terephthalic acid based PBT-b-FAD copolymers, synthesized under the same experimental procedure. A detailed analysis of PBF homopolymer confirmed its relatively high molecular weight, semicrystalline structure, and in consequence a very good mechanical performance. In turn an incorporation of FADD amorphous segments between PBF blocks resulted in multiblocked structure with the ester group links and the real composition very close to those calculated theoretically. Although the specific furan ring architecture disturbs the macromolecules symmetry, thus the crystallization process, the PBF-b-FAD copolymers, varying in between 20 and 80 wt% of the rigid segments, reveal the heterogeneous microstructure. And the phase separation may be enhanced by the annealing above Tcc. In consequence the furan-aromatic copolyesters combine a variety of physical properties (also the elastomeric behavior), tunable by both PBF to FAD ratio and the thermal treatment, with a good processability. They are also characterized by almost twice higher level of the tensile stress and E modulus when compared to previously reported PTF-b-FADD copolymers. Considering the soon commercialization of bio-1,4-butanodiol the presented materials have also a potential to be synthesized as fully bio-based.