Squid Beak Inspired Cross-Linked Cellulose Nanocrystal Composites

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomimetics

Background:

• Squid beaks exhibit unique water-enhanced mechanical gradient properties.
• Developing bioinspired materials with tunable mechanical responses is crucial for advanced applications.
• Cellulose nanocrystals (CNCs) offer a sustainable and versatile building block for nanocomposites.

Purpose of the Study:

• To create bioinspired cross-linked polymer nanocomposites mimicking squid beak mechanical properties.
• To investigate the impact of cross-link placement (matrix vs. matrix-filler) on wet mechanical performance.
• To explore the potential of these materials in biomedical applications.

Main Methods:

• Embedding functionalized CNCs (carboxylic acid- or allyl-) into an alkene-containing polymer matrix (P(VAc-co-VP)).
• Utilizing a photoinduced thiol-ene reaction with a tetrathiol cross-linker for cross-linking.
• Characterizing the wet mechanical properties, including modulus and swelling, under varying cross-linking strategies.

Main Results:

• Cross-linking both CNCs and the polymer matrix yielded higher wet mechanical contrasts (E'stiff/E'soft ≈ 20) compared to matrix-only cross-linking (E'stiff/E'soft ≈ 11).
• A significant increase in wet composite modulus was observed (14 MPa to 289 MPa at 37 °C) with allyl-functionalized CNCs.
• Reduced water swelling and enhanced wet modulus were attributed to the thiol-ene cross-linking network.

Conclusions:

• The placement of cross-links critically influences the wet mechanical properties of bioinspired nanocomposites.
• Achieving dual cross-linking (matrix and filler) unlocks superior mechanical tunability and contrast.
• These water-activated nanocomposites show promise for biomedical uses, including intracortical microelectrodes.