Photochemical Degradation of Disazo Dyes, R-Salt Derivatives, on Dyed Cotton

Abstract

Direct disazo dyes, R-salt derivatives, were synthesized and examined. The dyes were prepared by coupling of appropriate components with tetrazotized diacyl derivatives of aromatic diamines. Derivatives of dicarboxylic acids with the general formula HOOC―(CH2)n―COOH (n = 0 ÷ 4) were used as acylating agents. Photochemical degradation rates of dyes on dyed cotton fabric were studied. Compositions of azo-hydrazone tautomers, their aggregates, and their decay rates in UV-Vis light were determined. It was assumed that the length of aliphatic chain in the molecule affects the rate of its photochemical degradation T1/2, tautomeric composition, and dyes aggregation in azo and hydrazo forms.

Keywords

• aggregation
• azo-hydrazone tautomerism
• dicarboxylic acids amides
• direct dyes
• lightfastness
• photochemical degradation on cotton