Layered double hydroxides as alternative catalysts for furan-based polyesters synthesis

The development of alternative systems for the synthesis of furan-based polyesters is essential for enabling sustainable and biobased polymer production. In this work, layered double hydroxides (LDHs) containing alternative divalent (Zn^2 +, Sn²⁺), trivalent (Sb³⁺) and tetravalent (Ti⁴⁺) metals to the traditional Mg²⁺ and Al³⁺ were synthesized and employed as catalysts for the production of poly(ethylene furanoate) (PEF) through a two-stage melt polymerization process. The X-ray diffraction data of the LDHs indicate the correct formation of crystalline structure. The catalytic performance of the LDHs was evaluated and compared to that of conventional metal catalysts. Zn/Sn/Al- and Mg/Al/Ti-based LDHs were efficient catalysts in the polymerization reaction. Interestingly, commercially available Mg/Al-based hydrotalcite afforded PEF with the highest molecular weight. Thermal properties of PEF were determined by thermogravimetric analysis and differential scanning calorimetry. All the synthesised polyesters are amorphous, exhibiting high Tg (83–87 ºC). The scalability and versatility of LDH-based catalysts were demonstrated by producing furan-based polyesters at different scales and with varying diol chain lengths from 4 to 6 carbons. The formation of poly(butylene furanoate) (PBF), poly(pentylene furanoate) (PPeB), and poly(hexylene furanoate) (PHF) was confirmed by IR and ¹H NMR. These results underscore the potential of LDHs as sustainable catalysts for advancing greener polymerization technologies.