Shape‐Memory Photonic Thermoplastics from Cellulose Nanocrystals

Abstract

Responsive materials prepared using shape‐memory photonic crystals have potential applications in rewritable photonic devices, security features, and optical coatings. By embedding chiral nematic cellulose nanocrystals (CNCs) in a polyacrylate matrix, a shape‐memory photonic crystal thermoplastic (CNC‐SMP) allows reversible capture of different colored states is reported. In this system, the temperature is used to program the shape‐memory response, while pressure is used to compress the helical pitch of the CNC chiral nematic organization. By increasing the force applied (≈140–230 N), the structural color can be tuned from red to blue. Then, on‐demand, the CNC‐SMP can recover to its original state by heating it above the glass transition temperature. This cycle can be performed over 15 times without any loss of the shape‐memory behavior or mechanical degradation of the sample. In addition, multicolor readouts can be programmed into the chiral nematic CNC‐SMP by using a patterned substrate to press the sample, while the glass transition temperature of the CNC‐SMP can be tuned over a 90 °C range by altering the monomer composition used to prepare the polyacrylate matrix.

Bioinspired Colloidal Photonic Composites: Fabrications and Emerging Applications

“…[78] In some cases, inverse opal skeleton templates can also be used to produce CPCs by duplicating opal templates with other materials. [80] For example, Chen et al fabricated a flexible CPC by introducing a pregel solution into a TiO 2 inverse opal skeleton template, followed by photopolymerization (Figure 7b). [61b] The filling of high polymer content ensures the excellent flexibility and functionality of the inverse opal skeleton structured CPCs.…”

Current international research into cellulose as a functional nanomaterial for advanced applications

“…The resulting composite elastomer presented clear mechano-chromic behavior upon stretching, visible in ambient light and solely caused by the compression of the pitch in the direction perpendicular to the applied stretch (and not simply relying on birefringence-induced Newton colors like in many other existing reports). A recent follow-up from the same authors proposed the fabrication of similar elastomers with additional shape-memory properties [399].…”

Responsive Chiral Photonic Cellulose Nanocrystal Materials

“…Boott and co‐workers reported a shape memory photonic crystal (CNC‐SMP) comprised of CNC, 2‐ureido‐4[1H]‐pyrimidinone methyl acrylate, and elastomer, showing both shape and color change between the permanent and temporary states (Figure 10b). [ 162 ] Once equilibrating at 100 °C, the film was pressed and cooled to room temperature while maintaining the pressure (Figure 10c). After removing the pressure, the composite remained in the temporary pressed shape and blue‐shifted color.…”