Self-Healing Composite Coating Fabricated with a Cystamine Cross-Linked Cellulose Nanocrystal-Stabilized Pickering Emulsion

• Published in: Biomacromolecules Vol. 25; no. 2; pp. 715 - 728
• Main Authors: Xu, Guofan, Onyianta, Amaka J., Eloi, Jean-Charles, Harniman, Robert L., Laverock, Jude, Bond, Ian, Diejomaoh, Onajite Abafe, Koev, Todor T., Khimyak, Yaroslav Z., Eichhorn, Stephen J.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12.02.2024
• Subjects: Cellulose - chemistry; Cystamine; Emulsions - chemistry; Linseed Oil; Nanoparticles - chemistry; Water - chemistry
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/acs.biomac.3c00915

A gelled Pickering emulsion system was fabricated by first stabilizing linseed oil droplets in water with dialdehyde cellulose nanocrystals (DACNCs) and then cross-linking with cystamine. Cross-linking of the DACNCs was shown to occur by a reaction between the amine groups on cystamine and the aldehyde groups on the CNCs, causing gelation of the nanocellulose suspension. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the cystamine-cross-linked CNCs (cysCNCs), demonstrating their presence. Transmission electron microscopy images evidenced that cross-linking between cysCNCs took place. This cross-linking was utilized in a linseed oil-in-water Pickering emulsion system, creating a novel gelled Pickering emulsion system. The rheological properties of both DACNC suspensions and nanocellulose-stabilized Pickering emulsions were monitored during the cross-linking reaction. Dynamic light scattering and confocal laser scanning microscopy (CLSM) of the Pickering emulsion before gelling imaged CNC-stabilized oil droplets along with isolated CNC rods and CNC clusters, which had not been adsorbed to the oil droplet surfaces. Atomic force microscopy imaging of the air-dried gelled Pickering emulsion also demonstrated the presence of free CNCs alongside the oil droplets and the cross-linked CNC network directly at the oil–water interface on the oil droplet surfaces. Finally, these gelled Pickering emulsions were mixed with poly­(vinyl alcohol) solutions and fabricated into self-healing composite coating systems. These self-healing composite coatings were then scratched and viewed under both an optical microscope and a scanning electron microscope before and after self-healing. The linseed oil was demonstrated to leak into the scratches, healing the gap automatically and giving a practical approach for a variety of potential applications.