Self-Assembled Gels of Cellulose Nanocrystals for Diffusion-Controlled Color Switching

We demonstrate a new method to control the diffusion of guest molecules within cellulose nanocrystal (CNC) matrices containing embedded receptors. Specifically, we modified the structural composition of the guests by connecting them to polymer chains or nanoparticles, to slow down their diffusion rate, leading to controlled and colorful host–guest self-assembly processes within CNC-based materials. Moreover, considering the differences in guest binding affinity, we successfully built a supramolecular system that can exhibit macroscopic color changes by a sequenced exchange process. This system has been implemented in a spontaneous color-evolving film. We anticipate that these materials may be valuable to design a set of self-responsive materials and size exclusion gels functioning as, for example, time-evolving coatings, sustained-releasing materials, and separation columns.