Effect of Itaconic Acid As a Co-Monomer in Bio-Based Thermosets from Birch Bark

Plastic pollution is a pressing issue that threatens ecosystems around the world. Many commonly-used plastics have long lifetimes and are often discarded in the environment. Additionally, plastic manufacturing taxes the environment and diminishes natural resources. Thus, developing bio-based alternatives to petroleum-derived plastics is a promising approach towards lessening the adverse environmental impacts of plastic use. This study focuses on the valorization of betulin, a pentacyclic triterpenol, which can be extracted in high quantities from birch bark. Previously, we incorporated betulin into a series of polyester networks with bio-based diacids of varying chain length. We now extend this study to investigate the effect of itaconic acid as a co-monomer in these thermosets, which are formed using glycerol as the crosslinker. We use dynamic mechanical analysis to examine thermomechanical properties and thermogravimetric analysis to investigate degradative temperatures. Results show structure-property trends in which shorter diacid chain lengths and the presence of crystallinity lead to higher dynamic moduli and glass transition temperatures. In addition, these thermosets exhibit thermal stability until at least 298 °C in both inert and oxidative environments. Furthermore, the accelerated hydrolytic degradation of these samples will be presented. This work is part of a larger study to develop and evaluate bio-based plastics at all stages of life, from monomer extraction, to polymer synthesis, to end of life. These results demonstrate that thermosets with promising and tunable properties can be synthesized using betulin and other co-monomers.