Poly(acrylic acid)-grafted cellulose nanocrystal reinforced supramolecular adhesives: Ultrahigh strength, humidity resistance, and pH-controlled recyclability.

Bio-based adhesives have drawn growing attention due to the environmental and ecological issues posed by petroleum-based adhesives. However, their practical applications remain constrained by the limited adhesion strength and insufficient humidity intolerance. Herein, we have developed a bio-based adhesive using poly(acrylic acid)-grafted cellulose nanocrystals (CNC-PAA) and poly(vinyl alcohol) (PVA) through the construction of highly dense non-covalent supramolecular networks. The abundance of active groups and improved cohesion endow the PVA/CNC-PAA adhesive excellent adhesion to diverse substrates, with a strength exceeding 7.52 MPa for ceramics. The rigid network structure and hydrophilicity of CNC-PAA markedly improve the adhesive's stability and humidity resistance, enabling it to retain 75 % of its maximum adhesion strength even at 100 % relative humidity. Furthermore, the high density of hydrogen bonding and structured water allow the adhesive to maintain excellent adhesion at -196 °C. By modulating the hydrogen bonding via pH adjustment, this adhesive also exhibits on-demand adhesion-dispergation and recyclability. In addition, its bio-mass framework renders the adhesive biodegradable character. This work provides a novel approach for developing bio-based adhesives with high adhesion strength, humidity-resistance, and on-demand debonding properties, paving the way for sustainable adhesives in packaging, labeling, cryogenic, and other applications.