Unravelling the para- and ortho-benzene substituent effect on the glass transition of renewable wholly (hetero-)aromatic polyesters bearing 2,5-furandicarboxylic moieties

High-glass transition thermoplastic polymers have dawned much attention in recent years due to their typical stiffness, enhanced thermal properties, and more importantly the emerging need to replace commercial fossil-based products by more sustainable alternatives, derived from renewable resources. In this regard we engineer here for the first time the design of wholly (hetero-)aromatic polyesters based on a key-platform chemical-2,5-furandicarboxylic acid (FDCA) and commercially-available catechol, or hydroquinone, whose structures were characterized by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). Both polymers had a high glass transition (Tg up to 167 °C) detected by differential scanning calorimetry (DSC) and has excellent thermal stability according to thermogravimetric analysis (TGA). The para- and ortho- substitution in hydroquinone and catechol, respectively, affected crystallinity, which was typically higher for poly(1,4-phenylene-2,5-furandicarboxylate) (PHQF) favouring a stiffer and close packing structure. Also, the thermal properties were higher for PHQF.