Environmentally friendly coloration of cotton by the UV-induced photografting of alpha-bromoacrylamido dyes

Abstract

Conventional wet dyeing based on dye diffusion and adsorption in water requires large amounts of salt, time, and energy. alpha-Bromoacrylamido dyes are photografted onto cotton at room temperature as an environmentally friendly coloration process. Dye-originated radicals are produced by the photoscission of the carbon-sulfur and carbon-bromine bonds of the dyes and subsequently abstract hydrogen atoms to generate cellulose radicals which can initiate graft copolymerisation. About 88% of the dyes are polymerised, and the degree of polymerisation is estimated to be 12.7 or more, which was substantiated by mass and elemental analyses. The colour yield of the photografted cotton is seven times higher than that of conventional dyeing. Furthermore, good colour fastness properties are attributed to the water-insoluble polymeric dyes formed.