Digital color in cellulose nanocrystal films

Area of Science:

• Materials Science
• Biomaterials Science
• Nanotechnology

Background:

• Cellulose nanocrystals (CNCs) are derived from renewable resources and exhibit unique self-assembly properties.
• CNCs form chiral nematic liquid crystalline phases in aqueous suspensions.
• Evaporation of water from CNC suspensions can preserve these ordered structures into solid films.

Purpose of the Study:

• To investigate the relationship between CNC size distribution and the optical and structural properties of CNC films.
• To understand how CNC polydispersity influences the self-assembly process and multidomain color formation.
• To correlate microstructural characteristics with the observed iridescent coloration in bioinspired structural films.

Main Methods:

• Preparation of cellulose nanocrystal (CNC) suspensions with varying size distributions.
• Fabrication of CNC films by controlled water evaporation.
• Microreflection spectroscopy to analyze the directional coloration of the films.
• Transmission electron microscopy and other techniques to analyze the helicoidal nanostructure.

Main Results:

• The iridescent colors of CNC films are strongly dependent on the polydispersity of the CNC size distribution.
• Higher CNC polydispersity leads to less ordered nematic layers and affects multidomain color formation.
• The self-assembly process is significantly influenced by CNC size distribution, impacting the final film microstructure.
• A correlation was established between the helicoidal nanostructure and the observed directional coloration.

Conclusions:

• CNC size distribution is a critical factor controlling the self-assembly behavior and resulting optical properties of CNC films.
• Controlling CNC polydispersity offers a pathway to tune the structural coloration and microstructure of bioinspired materials.
• These findings advance the understanding of self-assembly in CNC systems for applications in structural color and advanced materials.