Redox-activity of polydopamine for ultrafast preparation of self-healing and adhesive hydrogels

The high adhesive property of polydopamine (PDA) has spurred various hydrogels for biological and medical applications. Herein, a dual-catalytic redox system was constructed by using the inner dynamic redox-activity of PDA and free radical initiator ammonium persulfate (APS) to initiate the polymerization of acrylic acid (AA) monomer to obtain Fe-PDA hydrogels within 2 h at room temperature. Fe-PDA NPs functions as both initiator to activate APS to generate free radicals and promotes the formation of the hydrogel and dynamic cross-linking mediator between the polymer chains. The tensile strength and ductility of the obtained hydrogels vary with the content of Fe-PDA NPs. Hydrogel with 0.15 wt% of Fe-PDA NPs has the highest tensile strength (~0.62 MPa) and hydrogel with 0.6 wt% of Fe-PDA NPs has the highest elongation, about ~650%. The introduction of PDA NPs imparts PAA hydrogel with reproducible adhesive properties and self-healing ability. The doped iron ion further endows hydrogel enhanced photothermal properties (up to 160 ℃ with 808 nm laser irradiation for 120 s) and conductivity. [Display omitted] •Rapid hydrogel formation at room temperature.•Fe-PDA nanoparticles function as both cross linker and initiator in the hydrogel.•Reduced catechol and quinone oxide endow polydopamine excellent redox properties.•Fe3+ ions enhance photothermal and endow electrical conductivity.