PEROXIDASE-CATALYZED SYNTHESIS OF LIGNIN PHENOL COPOLYMERS

Horseradish peroxidase catalyzes the copolymerization of phenols with kraft lignin in aqueous-organic solvent mixtures. Nearly all of the li gnin and over one-third of the phenol (either p-cresol or p-phenylphen ol) is incorporated into the copolymer which is highly insoluble in di methylformamide (DMF), presumably because of crosslinking of lignin mo lecules via polyphenol bridges. The copolymer consists of 80% lignin, by weight. In the absence of a phenol, lignin is polymerized into a no ncrosslinked, DMF-soluble material. Thermal analysis shows that the co polymerization of phenols with lignin results in a material with marke dly lower glass transition temperatures and higher (and more uniform) curing exotherms. The materials appear to act as thermosets and may ha ve application as replacements of conventional phenolic resins.