INTERFACIAL COVALENT CHEMICAL BONDING: TOWARDS THERMOREVERSIBLE ADHESION

Many industrial sectors like automotive and aeronautic industries are moving toward the use of multi-material devices and composite materials. Reversible adhesion becomes then increasingly important as it allows to structurally join dissimilar materials and keep them together during the material’s useful life, while allowing the easy repair of damaged parts or recycling of raw materials. One way to achieve this property is by thermoreversible covalent bonding based on Diels-Alder and its retro Diels-Alder reaction. This “click” reaction occurs between a diene and a dienophile to form an adduct at a certain temperature, then this adduct can be dissociated on command by simple heating. The investigation of the adduct dissociation via retro Diels-Alder reaction is key in understanding the adhesion reversibility based on these systems. In this work an already formed Diels-Alder adduct is synthesized then grafted on plasma polymer coatings or self assembled monolayers. These two different types of surfaces offer different environments for the molecules. Afterwards, a protocol for reaction monitoring based on TOF-SIMS spectroscopy was developed which allowed the determination of kinetic and thermodynamic parameters of the interfacial reaction on both surfaces. The effect of the adducts environment on the reaction was then elucidated by comparing the obtained values. Investigation of the same reaction in solution using 1H NMR spectroscopy confirmed the observations made on the effect of molecules immobilisation on the reaction. Essentially, the more the molecules are immobilized the lower is the energy barrier and the higher is the entropy contribution. Finally, the feasibility of interfacial adhesion based on this system was explored.