Polyguaiacol: a Useful Model Polymer for Lignin Biodegradation Research

A polymer of ring-labeled ¹⁴C]o-methoxyphenol (¹⁴C]guaiacol) was prepared by peroxidase-H₂O₂-catalyzed oxidation of the ¹⁴C-labeled monomeric compound. The ring-labeled ¹⁴C]polyguaiacol contained 67.71% carbon, 5.09% hydrogen, 27.49% oxygen, 25.44% methoxyl, and 8.60% phenolic hydroxyl. The polymer had an average molecular weight of between 5,000 and 15,000, as determined by gel chromatography. A schematic representation of the polymer, similar to previously published structures of polyguaiacols, was devised to meet these and other analytical parameters. The polymer is primarily composed of o-o and p-p-linked guaiacol moieties, with an occasional o-p-biphenyl link and some p-diphenoquinone structures. An approximate molecular formula is C₄₉O₁₄H₃₁]_n, where n 5.8. Its C₆ formula is C₆H_2.3O_0.3^carbonyl (OH)_0.7(OCH₃)_1.0. Polyguaiacol has many of the characteristics of a synthetic lignin. It is easier and less expensive to prepare than standard synthetic lignins (dehydrogenation polymers of coniferyl alcohol). It is degraded (¹⁴C]polyguaiacol → ¹⁴CO₂) by the lignolytic system of the white-rot fungus Phanaerochaete chrysosporium. It is suggested that ¹⁴C]polyguaiacol may be of value as a substrate for lignin biodegradation research.