Lignin selective dyes: quantum-mechanical study of their characteristics

The mechanism of dye-bonding to the lignin component of the fibre was checked using the quantum-mechanical and crystallographic approach. The calculated data support the conclusion that for the selectivity of cationic dyes for lignin, a high partial negative charge on accessible substituents on the periphery of the molecule is the most important, but not an exclusive factor. Besides the delocalized positive charge, what is also important for the interaction of a dye with hemicellulose, is the dye’s ability to be involved in hydrogen bonds, whereas for the interaction with lignin also its ability of stacking to it.