Preparation and Underwater Adhesion Properties of Bi-continuous Phases-Toughened Ionogel

Ionogel adhesives composing of rigid liquid-crystal phase and flexible percolating phase were fabricated through a free radical polymerization-induced microphase separation process. Incompatible 2-methoxyethylacrylate (MEA) and 2-(perfluorooctyl)ethyl methacrylate (FMA) monomers were chosen for copolymerization in a mixed ionic system to synthesize the ionogel. The microphase separation and reversible noncovalent interactions in the ionogel were finely tuned by adjusting the component ratios of FMA to ionic liquid (IL), aiming to form the unique bi-continuous phase structure. The results demonstrate that the bi-continuous phases provide a high fracture energy barrier to the polymer networks of ionogel, resulting in a high fracture toughness (24.2 kJ/m²) and an excellent fracture strength (1.76 MPa). More importantly, the hydrophobic bi-continuous phases with abundant noncovalent interactions can not only remove the hydration layer of substrate surface, but increase the cohesion and adhesion interactions of polymer networks, leading to a high interfacial adhesion toughness (up to 2260 J/m²) to different substrates and a brilliant fatigue threshold of interfacial adhesion (558 J/m²) in aquatic environment. It is believed that such an ionogel may shed light on advancing the exploitation of underwater adhesive materials with tough adhesion.