Anisotropic cellulose nanocrystal composite hydrogel for multiple responses and information encryption

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Anisotropic composites featuring cellulose nanocrystals (CNCs) are gaining interest for their unique optical characteristics.
• Well-ordered CNCs are key to achieving advanced material properties.

Purpose of the Study:

• To fabricate a multi-functional hydrogel with nematic CNC organization.
• To investigate the hydrogel's optical properties and stimuli-responsive behavior.
• To explore applications in environmental monitoring and anti-counterfeiting.

Main Methods:

• Fabrication of a polyvinyl alcohol (PVA)/CNC composite hydrogel via sequential soaking in salt solutions and DI water.
• Utilizing the Hofmeister effect and hydrophobic interactions to tune hydrogel properties.
• Employing local solvent displacement for patterned hydrogel creation.

Main Results:

• Achieved observable birefringence in the hydrogel through interference colors.
• Demonstrated enhanced mechanical strength and stimuli-responsive behavior to ion strength and pressure.
• Successfully created encrypted patterns observable only between crossed polarizers.

Conclusions:

• The developed hydrogel exhibits tunable optical properties and stimuli-responsiveness.
• Aligned CNCs significantly contribute to the hydrogel's enhanced mechanical and optical performance.
• The hydrogel shows potential for environmental monitoring and anti-counterfeit applications.