Fully Biomass-Derived Poly(oxanorbornene) Derivatives with Exceptional Mechanical Properties

Biomass-derived polymers with superior mechanical properties are essential for advancing sustainable alternatives to petroleum-based plastics. Despite the structural diversity and availability of biomass-derived monomers, poly(oxanorbornene) derivatives remain underexplored as candidates for high-performance materials. Herein, we report the facile synthesis and exceptional mechanical properties of fully biomass-derived poly(oxanorbornene) derivatives, incorporating biomass alcohol side chains and carboxylic acids within each monomer unit. High molecular weight polymers (Mn > 400,000) were synthesized via ring-opening metathesis polymerization (ROMP) of exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride in N,N-dimethylformamide (DMF), followed by the alcoholysis to introduce methyl, ethyl, and n-butyl side chains. Remarkably, the methyl-substituted polymer (OxMe) exhibited a tensile strength of 88 MPa despite a moderate glass transition temperature (Tg = 86 °C), deviating from the typical linear correlation between tensile strength and Tg observed in conventional amorphous polymers. Rheological analysis revealed that the oxanorbornene backbone contributes to a lower activation energy compared to its norbornene counterpart. In addition, poly(oxanorbornene) derivatives demonstrated versatile potential applications including fiber formation, thermal reprocessing, and hot-melt adhesives. Our findings establish poly(oxanorbornene) derivatives as promising fully biomass-derived high-performance polymers.