Exploring the Potential of High Molar Mass Poly(hydroxymethylfuroate): Synthesis, Properties, and Recyclability Studies

The synthesis of the fully furan-based high-molar-mass poly(hydroxymethylfuroate) (HMM-PHMF) is herein presented along with the investigation of thermal properties, filmability, water contact angle (WCA), and recyclability. The polymer (Mn > 200000 g mol-1) has been produced on a multigram scale by N-heterocyclic carbene (NHC)-promoted chain extension of PHMF (1 h, 190 °C), which can be directly synthesized from 5-(hydroxymethyl)furfural (HMF) or 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). The polyester is thermally highly stable up to 280 °C, showing a semicrystalline behavior with Tm ∼ 194 °C when processed from solvent and an amorphous character with Tg ∼ 90 °C when processed from the melt. HMM-PHMF has been efficiently filmed by compression molding and submitted to WCA analyses (86 ± 2°), behaving as a potential biobased food packaging material. Finally, recyclability has been assessed through alkaline hydrolysis producing HMFCA and cyclodepolymerization affording the starting hydroxymethylfuroate macrocyclic oligoesters c(HMF)n, which can be converted again through entropically driven ring-opening polymerization (ED-ROP), in a closed-loop cycle.