MALDI-TOF and 13C NMR analysis of a renewable resource additive-Thermoplastic acetylated tannins

- Mimosa tannin was acetylated to a water insoluble thermoplastic material of melting point 154 °C.
- By MALDI analysis the acetylated tannin is composed of oligomers of different levels of acetylation.
- All the different OH groups of the flavonoids, both phenolic and alcoholic, are subject to acetylation as observed by MALDI and 13C NMR.
- For mimosa tannin the predominance of acetylated robinetinidin units is due to robinetinidin predominance in the original tannin.

Acetylation of mimosa flavonoid tannin is easy to occur but to proceed to completion needs the presence of a catalyst. The acetylated tannin has been shown to be composed of flavonoid oligomers of different levels of acetylation in which the robinetinidin flavonoid unit predominates. All the different OH groups of the flavonoids, both phenolic and alcoholic, are subject to acetylation. Whatever the level of acetylation the acetylated tannin loses its solubility in water and becomes thermoplastic. In the case of the mimosa extract used here the predominance of acetylated B-flavonoid units is exclusively due to the predominance of B-type units, both robinetinidin and catechin, in the original tannin.