Structural coloration of chitosan-cationized cotton fabric using photonic crystals

Conventional textile coloration is a wet process involving high levels of water and chemicals consumption and wastewater generation. However, colour in textiles can also be generated by other mechanisms such as: absorption, emission, diffraction, interference and photochromism.[1] Chromotropic effect refers to reversible colour transformation due to external chemical or physical influence.[2] Photonic crystals are an important class of chromotropic materials. Colloidal crystals with a periodicity on the scale of half the wavelength of visible light exhibit structural colours similar to natural opals due to a diffraction effects that result in the appearance of a photonic band gap that forbids propagation of certain wavelengths.[3] Structural colouration is emerging as an innovative technology to produce colourful textiles materials.[4] Various colours impossible to reproduce by chemical coloration can be created by modifying the periodicity of the nanostructures or the environmental conditions using a single material.[5, 6] Photonic crystals can be applied on textile fabrics by colloid self-assembly and the structural colours can be controlled by adjusting the microspheres size and the viewing angles.[7] However, their application for textile structural coloration has been barely reported.[8] In this work, P(St-MMA-AA) composite nanospheres were deposited onto chitosan-cationized woven cotton fabrics. The structural colours of the deposited photonic crystals on the fabrics and its washing fastness were investigated.