Interplay between crystallization and the Diels–Alder reaction in biobased multiblock copolyesters possessing dynamic covalent bonds

Abstract

A series of biobased poly(2,5-furandimethylene succinate)-b-poly(butylene succinate) (PFS-PBS) multiblock copolyesters containing furan in the polymer main chains was synthesized, in which the thermo-reversible network structures are established via the furan/maleimide Diels–Alder (DA) reaction using bismaleimide (BMI) as a cross-linker. First, the DA reaction kinetics of PFS/BMI was investigated by in situ Fourier transform infrared spectroscopy (FTIR). The corresponding reaction rate coefficients at variable temperatures and the activation energy of the DA reaction were calculated. Furthermore, the interplay between crystallization and the DA reaction was studied combining differential scanning calorimetry (DSC) and in situ FTIR. The crystallization is suppressed by the DA reaction due to confinement of the formed DA network structure. On the other hand, the crystallization effect on the DA reaction is related to the FS sequence length of the copolyesters. The restriction effect of crystallization on the DA reaction is clearer in PFBS random copolyesters with a shorter FS sequence length than that in PFS-PBS multiblock copolyesters with a longer FS sequence length. Finally, the mechanical properties of PFS-PBS/BMIs were studied. The formation of a DA network structure significantly increases the modulus and tensile strength of PFS-PBS/BMIs despite the reduction in crystallinity. PFS-PBS/BMIs can be adjusted from soft to rigid and brittle materials by simply controlling the PFS and BMI content.