Peroxidase-catalyzed copolymerization of syringaldehyde and bisphenol A

Syringaldehyde, one of the major derivatives of lignin, was copolymerized with bisphenol A via a CiP (Coprinus cinereus peroxidase)-catalyzed reaction. Although syringaldehyde was not polymerized to a solid polymer, the copolymer with bisphenol A was obtained as a dark brown powdery precipitate. The relatively hydrophobic solvent, 2-propanol, gave a better yield (yield = 95%) than hydrophilic solvents, such as methanol, ethanol or acetone. Characteristic signals corresponding to the aldehyde group of syringaldehyde in the copolymer were detected in the FT-IR and C-13 NMR spectrum. The ratio of syringaldehyde incorporated into the copolymer was estimated by measuring the amount of monomers consumed (syringaldehyde and bisphenol A), which proportionally increased up to 80 mol% on increasing the initial ratio of syringaldehyde to bisphenol A. TGA (thermogravimetric analysis) showed that the thermally crosslinked copolymer (syringaldehyde:bisphenol A = 1: 1, w/w) had a much higher thermal resistance to thermal degradation than poly(bisphenol A); 36% residue still remained under a nitrogen atmosphere, even over 800 degrees C. This implies that the copolymer of syringaldehyde and bisphenol A could be a new thermally stable material originating from renewable resources. (C) 2009 Elsevier Inc. All rights reserved.