The need for sustainable polymers has driven the development of an array of chemical and biological pathways to potential monomers derived from renewable sources.
1-5 Despite decades of innovation, low conversion efficiencies from raw lignocellulosic feedstocks persist.
6 Here we present a new class of renewable polymer precursors that can be produced from the hemicellulose fraction of lignocellulosic biomass in high yields using a previously described aldehyde-facilitated biomass pretreatment.
7–9 By leveraging the use of aldehydes with different functionalities, we can install targeted functional handles onto both sides of the hemicellulose-derived xylose—creating a tricyclic, difunctional structure that presents as a potential renewable monomer for high-glass transition bioplastic synthesis. Here, we demonstrate the use of an easily bio-sourced carboxylic acid-functionalized aldehyde (glyoxylic acid) to produce a novel, tricyclic, diacid precursor from xylan in unmodified biomass in 83% yield and directly from commercial xylose in up to 95% yield. Polycondensation of the corresponding diester with a range of diols yielded a family of amorphous polyesters with tough mechanical properties, high glass transition temperatures and good gas barrier properties. Selective chemical recycling of the polyesters was possible at high yields even from a mixed plastic waste stream via alcoholysis and hydrolytic stability studies reveal that the polyesters will break down in neutral water at room temperature after an initial lag period of 77 days, during which time the polyesters remain mechanically useful. Due to the transformation’s simplicity, techno-economic analysis shows that even production from commercial xylose could be cost competitive with fossil alternatives. Finally, we explore polymer chemistries beyond polyesters using alternative functionalities to carboxylic acids to expand material production opportunities from lignocellulosic biomass.
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