Mussel-inspired cellulose-based adhesive with underwater adhesion ability

Inspired by mussels, a new cellulose-based (CTP) adhesive was fabricated by simply blending via cellulose nanofibrils (CNFs), tannic acid (TA), and polyethyleneimine (PEI), where the preparation method was green, facile, and simple. The structure and properties were examined by FT-IR, TGA, XRD, SEM, lap shear tensile, and water absorption tests. The results showed that chemical bonds, hydrogen bonds, and chain entanglement were formed among CNFs, TA, and PEI. Compared with the CNF adhesive, the dry shear strength of the CTP adhesive increased 103% to 392.2 ± 32.2 kPa. And the wet shear strength of CTP adhesive increased from 0 kPa to 144.7 ± 20.1 kPa, indicating that the CTP adhesive can be used in humid or even water environments. Meanwhile, the water absorption of CTP adhesive decreased from 37.9 ± 14.1% to 12.8 ± 5.9%. It was the introduction of catechol groups and physical–chemical interactions of three components that endow the CTP adhesive with improved dry and wet adhesion strength and water resistance. Moreover, the proposed CTP adhesive could be used on the surface of various materials, including rubber, plastic, paper, wood, metal, and glass. Overall, this work shows that the CTP adhesive has a wide range of application prospects.