Journey to Polymeric Materials Composed Exclusively of Simple Lignin Derivatives

Abstract

Between 1955 and 1960, theories about lignin configuration were vacillating between random-coil and cross-linked “microgel” representations for macromolecular lignin chains. Light scattering was important in these early studies, but it was difficult to deal adequately with lignin fluorescence at the 546 nm incident wavelength being used. Cross-linking then prevailed, largely because of the hydrodynamic compactness of high molecular weight lignin species. The conceptual ramifications of this paradigm led to 40 wt % incorporation limits (or less) for lignins in cohesive polymeric materials. In due course, however, further evidence for a random-coil description of individual lignin components materialized; it became less obvious why simple lignin derivatives could not, on their own, form promising polymeric materials. The first plastics composed solely of a (native) ball-milled softwood lignin are similar to polyethylene in tensile behavior. Blending with just 5 wt % tetrabromobisphenol A (a flame retardant)...