Preparation, performance and application of photochromic thermal expansion microcapsules containing spiropyran in water-based ink

A novel type of photochromic thermally expandable microcapsules (PTEMs) were prepared through suspension polymerization. The shell material of the microcapsules consisted of acrylonitrile (AN), methyl methacrylate (MMA), and methyl acrylate (MA). The core material utilized n-hexane as a foaming agent containing photochromic dye (spiropyran). On the basis of the preparation, the investigation further focused on the chemical structure, surface morphology, particle size, color-changing ability, and thermal expansion of the microcapsules. Additionally, the PTEMs were used in water-based inks with good compatibility and for screen printing to obtain patterns. Meanwhile, the color changeability of the printed samples was evaluated using a portable colorimeter. Eventually, the results demonstrated that the printed products exhibited excellent color change and thermal expansion capabilities. In future, the PTEMs will have the potential to develop water-based ink applications in anti-counterfeiting and smart packaging.