Disperse Dyes Other Chromophores

All azo dyes contain one or more azo groups (-N=N-) as chromophore in the molecule on the basis of the number of azo groups in each molecule, they are named monoazo-, disazo-, trisazo-, etc. The azo groups are in general bound to a benzene or naphthalene ring, but they can also be attached to heterocyclic aromatic molecules or to enolizable aliphatic groups. On the basis of the characteristics of the processes in which they are applied, the molecule of the dye is modified to reach the best performances so they can be acid dyes, direct dyes, reactive dyes, disperse dyes, or others. 

Using these and other design principles, very large increases in the valnes of chro-mophores have been obtained since the original work on the simple red monoazo dyes of the disperse dye class. These new NLO chromophores are known as high pP chromophores , a selection of which are shown in Figure 5.31, the pP values quoted being measnred by electric field induced second harmonic at (EFISH) 1.9 It... 

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