Photoreversible Shape Memory Polyurethane Films Prepared Using Demulsification-Induced Fast Solidification for Multilevel Information Encryption Application

This study introduces waterborne polyurethane (WPU) films with defined shape memory and multistimuli responsive properties for information encryption. The shape memory feature is attributed to the semicrystalline structure of polycaprolactone (PCL) serving as the soft segment in the WPU. Incorporating the photoreversible moiety 9-anthracenemethanol (9-An) impacts photoresponsive characteristics and enhances the tensile strength of the film after 1 h of ultraviolet irradiation. The demulsification-induced fast solidification (DIFS) method offers rapid film preparation, controllable thicknesses, and multidimensional shapes, surpassing the conventional cast method. Cellulose nanocrystals (CNCs) render the WPU composite films solvent-sensitive, inducing color changes through cholesteric structure pitch alterations. The resulting combination of photo- and solvent-sensitivity with shape memory attribute positions the films as promising candidates for multilevel information encryption, offering an approach to functional polymer film development.