Unsaturated biobased polyesters from bicyclic α-pinene-based diols

Journal article, 2026

Here we report the synthesis and characterization of a set of four unsaturated prepolymers made from polycondensation of two (−)-α-pinene-derived bulky diols, trans-hydroxy nopol (HN) and trans-hydroxy myrtenol (HM), with dimethyl itaconate and dimethyl maleate as renewable acyl donors. Structure verification by ¹H and ¹³C NMR in concert with Fourier transform infrared analyses confirmed intact backbone C=C groups and ester formation in these prepolymers, showing number-average molar masses between 1.4 and 6.3 kg mol⁻¹ and dispersity in the range 1.3–2.2. The intact pinene core concomitant with the chiral arms protruding from it results in elevated thermal stability, manifested by 5% weight-loss temperatures (T₅) above 220 °C and decomposition maxima reaching 315 °C, concomitant with an elevated glass transition temperature for one of the materials (Tg of 45 °C). Finally, to investigate end-of-life options, subjecting the four polymers to depolymerization studies using the leaf-branch compost cutinase resulted in partial depolymerization for the less flexible maleate-containing polyesters, liberating the corresponding diol monomers (8% HN and 13.5% HM). Biodegradation was further supported by shifted SEC traces toward lower molar mass. Complementary in silico docking and metadynamics studies were used to identify near-attack conformations in which the ester carbonyl in the cis-alkene-containing, maleate-based bulky backbones is ready for hydrolysis. Overall, this study highlights the untapped potential to generate biobased unsaturated polyesters by capitalizing on rigid bicyclic terpene-based diols, resulting in elevated thermal performance while retaining enzymatic degradability. © 2026 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.