| 초록 |
We introduce a new colorimetric display technology in which cellulose nanocrystals (CNCs) self-assemble in suspension to form iridescent chiral nematic films. Iridescent CNC films reflect circularly polarized light at specific wavelengths in the dried film state. The chiral nematic pitch is tunable depending on the applied external energy during the suspension procedure, i.e., ultrasound. The reflection wavelength is electrostatic in nature, thus meaning that the electrostatic repulsion between CNCs is essential for determination of reflection wavelength. To figure out the underlying mechanism exactly, we controlled the surface charge density of CNCs by using 2,2,6,6-tetramethylpiperidine-1-oxyl radical mediated oxidation and explained how the electrostatic repulsion between CNCs could span the reflection wavelength in the film. Even more intriguing, the film was found to exhibit a shift of the Bragg reflection band when exposed to specific environment. |
