Cationic copolymerization of furfural and furfural-derived 3,4-dihydropyran: biobased and biodegradable polyacetals with high glass transition temperatures

• Cationic copolymerization of furfural and DHP using GaCl 3 /EtSO 3 H/1,4-dioxane resulting in alternating copolymers. • Enhanced yields (up to 72%) and controlled dispersity ( M w / M n 1.29–1.45). • Resulting poly(furfural- alt -DHP) copolymers show high glass transition (>160 °C). • Acid-triggered degradation of copolymer acetal moieties demonstrated. • Biodegradation of the copolymers in activated sludge (wastewater treatment) and soil is shown. This study addresses the challenge of directly polymerizing furfural, a renewable platform chemical, by cationic copolymerization of furfural and 3,4-dihydro-2H-pyran (DHP), which can be derived from furfural, using GaCl 3 /EtSO 3 H/1,4-dioxane. This approach achieves higher yields (up to 72 %) and improved dispersity ( M w / M n = 1.29–1.45) compared to BF 3 ·OEt 2 , yielding fully bio-based, predominantly alternating poly(furfural- co -DHP) copolymers with high glass transition temperatures ( T g > 160 °C). These materials, thoroughly characterized by 1 H, 13 C NMR and FTIR spectroscopy, GPC, TGA, and DSC, demonstrate a new pathway towards sustainable polyacetals. Further, we show that the materials undergo acid-triggered degradation, facilitated by the acetal linkages, and exhibit biodegradation in activated sludge (wastewater treatment) of ca. 52 % after 28 days (following OECD 301F), indicating their potential for reducing plastic waste accumulation and environmental persistence.