Patternable and Rewritable Retroreflective Structural Color Shape Memory Polymers

Abstract

The microstructure of the SMPCs is temporarily deformed under external force, and the color disappears or changes simultaneously; after release of the external force, the SMPCs recover to the original shape and color. [15] Therefore, they have attracted tremendous interests in patterning, especially, in rewritable and reusable photonic crystal structural color materials. [16] For example, Fang et al. reported a pressure-and ethanol-responsive inverse opal SMPC, which is patternable and reconfigurable. [11,17] Wang et al. reported a thermoresponsive inverse opal SMPC that can be used for rewritable photonic papers with capabilities of multicolor writing and pattern copying. [18] Nonetheless, the fabrication of inverse opal PCs is usually time-consuming and costly. And the current researches mainly focus on the selection of SMPs and selection of external stimuli, [19] little researches involve new shape memory structural color materials with new structural colors.Recently, we reported a retroreflective structural color film (RSCF) derived from the mechanisms of retroreflection and thin-film interference combined with total internal reflection (TIR), [1b] and Goodling et al. reported a structural color within a droplet caused by the mechanisms of TIR and interference. [20] Based on the recently reported structural color mechanisms and method, herein, we further report a new kind of shape memory retroreflective structural color film (SMRSCF). This SMRSCF can not only be facilely fabricated on a large scale but also easily prepared in monochromatic, polychromatic, complex, and stitched patterns through customizing the templates. Moreover, the pattern templates are reusable, and the SMRSCFs are erasable and rewritable. This new kind of shape memory retroreflective structure color materials and their fabrication method we present here may find more promising applications than the previously reported SMPC materials. Results and Discussion Fabrication and Characterization of the SMRSCFThe fabrication process of SMRSCFs is schematically illustrated in Figure 1a. Briefly, the RSCF template was fabricated and used to prepare the polydimethylsiloxane (PDMS) template (Figure S1a, Supporting Information). The mixture of prepolymer A and curing agent B was poured onto the PDMS template to obtain the SMRSCF after cured and peeled off Almost all the shape memory structural color materials are based on the photonic crystal color mechanism, and there remain great challenges such as iridescent colors, hard fabrication, etc. Herein, a new kind of shape memory retroreflective structural color film (SMRSCF) is fabricated through the "two-template" method, based on the mechanisms of retroreflection and interference combined with total internal reflection. Different from photonic crystal color shape memory materials, this new SMRSCF displays brilliant monochromatic, polychromatic, complex, and stitched patterns, respectively, depending upon the flexibly customized templates. The shape memory polymers can further endow the film with exce...

Responsive Structural Colors Derived from Geometrical Deformation of Synthetic Nanomaterials

“…Reproduced with permission. [ 75 ] Copyright 2021, John Wiley and Sons; c) The separation of the microspheres. Reproduced with permission.…”

“…Based on Wu's “two‐template” methods, a shape memory retroreflective SCM is prepared (see Figure 4b). [ 75 ] The variety of templates allows this SCM to display complex structural colors. According to the glass transition temperature, the geometry of the microspheres can be encoded by hot pressing, changing the path of total internal reflection.…”

Panther chameleon-inspired, continuously-regulated, high-saturation structural color of a reflective grating on the nano-patterned surface of a shape memory polymer

“…In the reported results, only limited color change has been achieved. 23,[34][35][36] For another thing, the brightness and saturation of structural color, which can be attributed to the following issues, need to be improved further. First, relative to two-and three-dimensional photonic crystal structures, a one-dimensional (1-D) grating exhibits much higher reectivity and higher color saturation because of the sufficient interference of reected light.…”

Recent Progress in Responsive Structural Color

“…Because of the deformation of the dome, the structural color of the pressed area disappears, resulting in patterned structural color. 95 On the basis of a similar strategy, Song et al presented a method to imprint robust invisible patterns in colloidal crystals of hollow silica spheres (Figure 3B). 96 The patterned (etched) regions and background areas have different wettability.…”

“…Wu et al used the patterned masks to press the shape memory retroreflective structural color film. Because of the deformation of the dome, the structural color of the pressed area disappears, resulting in patterned structural color . On the basis of a similar strategy, Song et al.…”