Azide Reactive Dyes Part II - Transfer-printing Properties of Sulphonyl- and Aryl-azide Dyes on Nylon 6.6

The transfer-printing properties of dyes containing the sulphonylazide (-SO₂N₃) and arylazide (ArN₃) groups have been examined for nylon 6.6 substrates. After sublimation at 200°C the azide group decomposes rapidly to a nitrene species which reacts with the polymer. Dye fixation occurs by insertion of the nitrene into the carbon-hydrogen bonds of the polymer, thus forming a nitrogen bridge. A competing reaction involves hydrogen abstraction from the substrate to give an amino derivative of the dye which is not covalently bound to the polymer. Fibre-grafting occurs to the extent of about 60–75% for both series of dyes. Unlike the sulphonylazides, the arylazide dyes show a pronounced colour change after transfer, as the thermally-generated amino group is directly conjugated with the dye chromogen.