Bio-based poly(butylene furandicarboxylate)-b-poly(ethylene glycol) copolymers: The effect of poly(ethylene glycol) molecular weight on thermal properties and hydrolysis degradation behavior

Abstract

Poly (butylene furandicarboxylate) based poly (ether ester), with poly (ethylene glycol) (PEG) molecular weight from 600 to 20 K g mol−1 and mass fraction of hard segments fixed at 50%, are synthesized through transesterification and melt polycondensation. When Mn (PEG) is less than 1500 g mol−1, the copolymers tend to be homogeneous. The tendency of microphase separation is facilitated by the increasing Mn (PEG). The mechanical properties and water swelling are influenced by Mn (PEG), equilibrium water-uptake and PEG crystals. Elastic modulus of samples with no PEG crystals vary from 34 to 64 MPa, with elongation at break exceeding 1000%. The hydrolytic degradation is strongly affected by Mn (PEG), degradation medium and alkalinity. The degradation of copolymers with short PEG (<1500 g mol−1) could be accelerated by ions and increasing alkalinity in medium. For copolymers with Mn (PEG) from 2 K to 6 K g mol−1, the degradation rate is relatively slow, due to relatively long PBF segments and improved PBF crystals hindering the hydrolysis of ester bond. For copolyesters of PBF50-PEG10K and 20 K, the oxidation of PEG dominates the degradation behavior while the PBF segments can hardly be damaged. The drastic degradation of these samples takes place in the solutions of pH = 12, suggesting the high alkalinity can break the long PBF segments. The distinct degradation behavior of the copolymers conduces to realize tuned hydrolysis for different biomedical applications. Keywords: Bio-based, 2,5-Furandicarboxylic acid, Poly(ether ester), Microphase separation, Tuned hydrolysis degradation