Synthesis and characterization of biobased (co)polyesters derived from cyclic monomers: camphoric acid and 1,4-cyclohexanedimethanol

Abstract

Annual plastic production volumes are more than 400 million tons and are anticipated to continue increasing over the next decade. The majority of plastics originate from fossil resources. Limited raw material reserves and ongoing utilization of plastics contribute to elevated CO₂ emissions, ultimately contributing to climate change. Development of green polymers (i.e., biobased) is one way to reduce our environmental impact. Using renewable resources as raw materials for polymer synthesis reduces the reliance on petroleum and in some cases enables recycling and/or biodegradation. Various aliphatic biobased polyesters have been studied; however, they typically have low glass transition temperatures (T_g) and poor thermomechanical performance, which may limit their applications. In this work, we investigate the synthesis route and structure–property relationships of (co)polyesters from cyclic biobased monomers, camphoric acid and 1,4-cyclohexanedimethanol (CHDM). We observed that increasing the reaction temperature and extending the reaction time led to increased molecular weight and yield of poly(cyclohexanedimethylene camphorate) (PCHC). Conversely, substituting p-toluenesulfonic acid (p-TSA) with a titanium(IV) isopropoxide (TTIP) catalyst led to reductions in both the molecular weight and yield. Furthermore, (co)polyesters with T_g values ranging from –29 to +56 °C were successfully synthesized. DSC and WAXD analyses suggest that the polyesters derived from camphoric acid and the linear diols were amorphous, whereas those based on CHDM were semicrystalline. This work helps address existing knowledge gaps in biobased polymer development by introducing cyclic biobased monomers that expand the current library of renewable materials, thereby broadening opportunities for advanced applications such as coating and packaging materials.