Bio-based waterborne polyurethane structural color films with high stability

In recent years, structural colors derived from photonic crystals (PCs) with a periodically ordered nanostructure are gorgeous and iridescent, but once their structure is destroyed, they will fade. In this work, the feasibility of the application of bio-based waterborne polyurethanes (WPU) in structural color films was explored. The structural stability of PCs is enhanced bio-based WPU as a kind of green product, which can replace solvent polyurethane one. A tung oil polyol (TOP) is fabricated by one-step method with simple purification process and used to prepare waterborne polyurethane dispersions (WPUD). More introduction of TOP into the WPUD may help improve tensile strength and hydrophobic capability. It shows excellent mechanical properties with 16.8 MPa in tensile strength and water contact angle 109.5 degrees. The SEM images confirmed that bio-based WPU is more conducive to the self-assembly of silica particles than traditional WPU. We used the dispersion of bio-based waterborne polyurethane and monodisperse silica to realize the self-assembly of colloidal particles under heating conditions, and successfully prepared structural color films with bright colors and stable structure.image