Photochromic microcapsules by coacervation and in situ polymerization methods for product-marking applications

Photochromic materials can change their colour quickly and reversibly when exposed to light of certain wavelengths. These materials have recently been of great interest for intelligent and functional textile applications. In this study, two different photochromic dyes, including 1 ',3 '-dihydro-1 ',3 ',3 '-trimethyl-6-nitro-spiro[2H-1-benzopyran-2,2 '-(2H)-indole] and 1 ',3 '-dihydro-8-methoxy-1 ',3 ',3 '-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2 '-(2H)-indole], were microencapsulated by coacervation and in situ polymerization methods. Ethyl cellulose and melamine-urea-formaldehyde were used as polymers. The Fourier transform infrared spectroscopy, particle size and size distribution analysis, scanning electron microscopy, and ultraviolet spectrophotometry evaluations were utilized to characterize the structure, morphology, size distribution, and absorbance maxima of the photochromic microcapsules. The results indicated that photochromic microcapsules were in spherical shape, smooth, and homogeneous characteristics. These microcapsules were applied successfully onto cotton fabric using printing technique. Then, the activities of photochromic microcapsules on the fabrics were analysed by colour analysis under different light sources, fatigue resistance, washing, and rubbing fastness tests. After printing, the colours of the fabrics changed very quickly under different light sources. At the same time, these fabrics showed a reversible photochromic response and good fatigue resistance. Mechanical and physical properties of the fabrics such as thickness, air permeability and tensile and tear strength were also investigated. It can be concluded that photochromic microcapsules are well appropriate for brand protection and prevention of imitation in textile materials.