Chromogenic Photonic Crystals Enabled by Novel Vapor-Responsive Shape Memory Polymers

Smart shape memory polymers (SMPs) can memorize and recover their permanent shape in response to an external stimulus, such as heat, light, and solvent. They have been extensively exploited for a wide spectrum of applications ranging from biomedical devices (e.g., surgical stents and sutures) and implants for minimally invasive surgery to aerospace morphing structures and self-healing materials. However, most of the existing SMPs are thermoresponsive and their performance is hindered by slow response speed, heat-demanding programming and recovery steps. In this manuscript, by integrating scientific principles drawn from two disparate fields that do not typically intersect - the photonic crystal and SMP technologies, we report a new type of SMP that enables unusual "cold" programming and instantaneous shape recovery triggered by exposing the samples to various organic vapors. These stimuli-responsive materials differ greatly from existing SMPs as they enable orders of magnitude faster response, striking chromogenic effects, and room-temperature operations for the entire shape memory cycle, promising for many applications ranging from reusable chromogenic vapor sensors to reconfigurable nanooptical devices. Moreover, this interdisciplinary integration provides a simple yet sensitive optical technique for investigating the intriguing shape memory effects at nanoscale.