Asger Holm Agergaard, Steen Uttrup Pedersen, Henrik Birkedal, Kim Daasbjerg
Catecholato-metal complexes are widely used in functional materials such as hydrogels, where the dynamic nature of the coordination bonds between catechol and metal ions contributes to self-healing and stimuli-responsive properties. Herein, we translate the pH-controlled speciation of such complexes known from bulk to a surface counterpart. We create catecholato-metal attachments by electrografting catechol to glassy carbon surfaces, enabling binding of Al3+ or Fe3+ and, subsequently, dopamine. When binding dopamine, pH determines whether bis- or tris-catecholato-metal species dominate. Polymer brushes of poly(methyl methacrylate) are grown from these attachments and subsequently detached by electro-oxidation of the catechol, causing the catecholato-metal complex to disintegrate. This study shows that the catecholato-metal complex retains its pH- and oxidation-responsive properties when confined to the surface, and that catechol-based polymer brush interfaces constitute a versatile approach toward on-demand renewal of smart surfaces.