Synthesis and Characterisation of Azo-Based Dichlorotriazine Reactive Dye with Halochromic Behaviour

Halochromism or pH sensitivity has tremendous potential for applications in various textile fields, such as protective clothing, wound dressings, etc. Reactive dye is mostly used to colour cotton or other regenerated cellulose fibres due to its better fastness and wide range of hue, from vivid to dull shades. In this research work, an azo-based dichlorotriazine reactive dye was synthesised from H-acid (4-amino-5-hydroxy-2,7-naphthalen-edisulfonic acid) and 4-nitroaniline, which incorporates a halochromic behaviour. The change of colour of this dye was evaluated both in the the solution stage and coloured fabric stage in various pH solutions. A visible change of colour with the alteration of pH was observed after dyeing textile fabric with the synthesised dye. However, a significant difference was observed in a few cases with regard to the change of colour with the alteration of pH in the solution stage and coloured fabric stage. The dyed fabric also displayed very good to excellent wash fastness properties. Generally, the reactive dye synthesised in this research demonstrated an obvious change of colour with the alteration of the pH level.