Bioinspired Biobased Elastomeric Adhesive Using Diels–Alder Chemistry
Tuhin Subhra Pal, Bhavya Parameswaran, Swarnav Koley, Nikhil K. Singha
Abstract
Inspired by the robust adhesion mechanisms of marine organisms, this study presents the development of catechol-modified, biobased elastomeric adhesives utilizing Diels–Alder (DA) “click” chemistry. Epoxidized natural rubber (ENR), a sustainable elastomer derived from natural rubber, was chemically modified to introduce furfuryl functionality, enabling dynamic cross-linking with a catechol-based cross-linker (DOPAMal: dopamine-maleimide). The resulting adhesive system combines the remarkable adhesion properties of catechol moieties with the thermal reversibility of DA chemistry, creating a unique platform for advanced adhesive applications. The thermo-reversible covalent bonds formed via DA chemistry were characterized using differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR) spectroscopy. The incorporation of the catechol-based DOPAMal into the polymer chains transformed the soft ENR into a more rigid material, as demonstrated by nanoindentation (NINT) analysis. The tensile study revealed a notable improvement in mechanical strength due to the formation of hydrogen bonding and dynamic covalent DA adducts. Adhesion strength and reusability were evaluated through lap shear tests, revealing strong bonding and remarkable recovery. The adhesives demonstrated excellent self-healing behavior, as confirmed by optical microscopy, with damage recovery attributed to dynamic covalent bonding and hydrogen bonding interaction. This system utilizes the reversible nature of Diels–Alder reactions in combination with the strong noncovalent interactions of catechol moieties to create adhesives with superior adhesion strength, thermoreversibility, and self-healing properties. These properties make the developed adhesives highly suitable for applications in coatings, biomedical materials, and other industries requiring durable yet reversible adhesive systems. The work establishes a versatile framework for incorporating bioinspired strategies into elastomeric materials, paving the way for sustainable and multifunctional adhesives.