Biobased Thermoplastic Elastomers: Structure-Property Relationship of Poly(hexamethylene 2,5-furanodicarboxylate)-Block-Poly(tetrahydrofuran) Copolymers Prepared by Melt Polycondensation

Abstract

A series of poly(hexamethylene 2,5-furanodicarboxylate)-block-poly(tetrahydrofuran) (PHF-b-F-pTHF) copolymers were synthesized using a two-stage procedure, employing transesterification and polycondensation. The content of pTHF flexible segments varied from 25 to 75 wt.%. 1H nuclear magnetic resonance (NMR) and Fourier transformed infrared spectroscopy (FTIR) analyses were applied to confirm the molecular structure of the materials. Differential scanning calorimetry (DSC), dynamic mechanical measurements (DMTA), and X-ray diffraction (XRD) allowed characterizing the supramolecular structure of the synthesized copolymers. SEM analysis was applied to show the differences in the block copolymers’ morphologies concerning their chemical structure. The influence of the number of flexible segments in the copolymers on the phase transition temperatures, thermal properties, as well as the thermo-oxidative and thermal stability was analyzed. TGA analysis, along with tensile tests (static and cyclic), confirmed the utilitarian performance of the synthesized bio-based materials. It was found that an increase in the amount of pTHF caused the increase of both number-average and weight-average molecular weights and intrinsic viscosities, and at the same time causing the shift of the values of phase transition temperatures toward lower ones. Besides, PHF-b-F-pTHF containing 75 wt.% of F-pTHF units was proved to be a promising thermoplastic shape memory polymer (SMP) with a switching temperature of 20 °C.

Influence of Rigid Segment Type on Copoly(ether-ester) Properties

“…Signals at 8.59, 8.07, and 7.98 ppm (f, g, h signals) on the 1 H NMR spectra of PHN can be ascribed to protons of naphthalene ring [ 21 ]. The signals originating from methylene protons of hexylene glycol units appear at 1.45, 1.77, and 4.33 ppm for PHF [ 22 ]. However, signals of methylene protons of hexylene glycol units slightly differ for other polyesters (PHT, PHN).…”

“…The 1 H NMR spectra of poly(ether-ester)s have four new resonance signals assigned to the protons of pTHF. Signal i is assigned to inner methylene protons of pTHF ether block at 1.6 ppm and outer methylene protons of ether block (signal k) that can be found at 3.42 ppm [ 22 , 23 ]. The last two new signals are caused by a transesterification reaction between polyesters and pTHF what leads to a change in resonance of methylene group proton in pTHF.…”

“…The most accurate copoly(ether-ester) is PHF-b-F-pTHF 50/50, which calculated composition differs only about 2,49% from the expected value. The difference can be caused by the introduction of additional pTHF, due to losses in the dosing of the viscous substrate and distillation of the reaction substrate under reduced pressure [ 22 ].…”

“…There are also characteristic bands of aromatic ring moieties shown near 724–764 cm −1 (ring out-of-plane deformation), 820–875 cm −1 (ring out-of-plane deformation), 1016–1130 cm −1 (ring in-plane deformation) [ 25 , 26 ]. Moreover, for PHF and PHF-b-F-pTHF signal associated at 1222 cm −1 , arising from the =C-O-C= furan ring vibration [ 22 ].…”

Degradable Elastomers: Is There a Future in Tyre Compound Formulation?

“…Goracy et al prepared a series of poly(ether-ester)s copolymers using monomers derived from renewable resources by a two-stage procedure, consisting of transesterification and polycondensation processes in the presence of Ti(OBu) 4 [ 53 ]. The multiblocks copolymers were constituted by a hard block made of poly(hexamethylene 2,5-furanodicarboxylate) (FHD) and poly(tetrahydrofuran) (F-pTHF) soft sequences ( Scheme 5 ).…”