Chemically Recyclable and Enzymatically Degradable Polyesters from α-Pinene-Derived Chiral Diols

Accelerated production of recyclable and biodegradable biopolymers is crucial in combating the socio-economic and environmental issues of fossil-based plastics. While renewable diacids have been in the spotlight for the generation of bio-based polyesters with tailored properties by varying the alkyl chain length, capitalizing on diols from biomass for this purpose is underexplored and has mainly focused on linear and branched shorter chain alcohols. Here we explored the potential of two (ꟷ)-α-pinene-derived diols (PDOs) as building blocks to generate polyesters that mimic the properties of aromatic fossil-based polymers when combined with renewable diesters. The semi-crystalline or amorphous nature of the resulting polymers is tunable with the appropriate choice of diester. We demonstrate a concise synthesis of two novel unsymmetrical chiral PDOs on 20-40 g scale, together with eight structurally differing polyesters with excellent thermal stability; as reflected by high melting (270 oC, 277 oC), and glass transition temperatures (90 oC, 121 oC) for two of the polymers. The steric hindrance of the intact bicyclic α-pinene ring structure protruding from the backbone of the polymers can also aid in the degradation process, manifested by facile chemical recycling of these polyesters under mild conditions to recover both monomers. Finally, our results show how the generated rigid polymers are prone to enzymatic degradation by PETase and cutinase without any chemical pre-treatment. Our results illuminate the potential of expanding the currently available chemical space in bio-based monomers to bicyclic diols to generate biomaterials with tailormade properties.