Investigating the Role of Molecular Structure on the Entanglement Behavior of Lignin-Derivable Polymethacrylates

Lignin-derivable polymethacrylates are an emerging class of biobased polymers with broadly tunable thermal and mechanical properties alongside inherent chemical recyclability. Several reports have described structure-property relationships for these materials, but despite potential promise in various polymer applications, relatively few studies have examined how the molecular structures of these materials translate to processing and performance (e.g., creep resistance, toughness, strength). Herein, we elucidate key structure-property-processing-performance relationships of three lignin-derivable polymers with differing ortho-methoxy content on the aromatic rings ─ poly(phenyl methacrylate) (PPhM), poly(guaiacyl methacrylate) (PGM), and poly(syringyl methacrylate) (PSM) ─ through rheological characterization across a broad molecular weight range. Notably, the critical entanglement molecular weights (M_cs) substantially increase with the number of methoxy moieties (PPhM < PGM < PSM), a trend that is attributed to increasing chain stiffness from bulkier repeat units. We also report Mark-Houwink parameters, enabling more straightforward characterization by conventional gel permeation chromatography methods for absolute molecular weight determination, as well as calculation of intrinsic viscosities for solution processing. Overall, this work provides a foundation for the elucidation of structure-property-processing-performance relationships in emerging biobased materials, facilitating the translation of high-performance, lignin-derivable polymers with broadly tunable rheological profiles from the laboratory toward industrial application.