Fabrication Of Electroless Copper-plated Composites By Dopamine Surface Functionalization

Marine mussels could firmly attach to all kinds of wet surfaces by secreting adhesive proteins. Inspired by these protein-based adhesives, it was found that an adherent polydopamine layer could be formed on virtually all types of organic and inorganic materials via spontaneous oxidative self-polymerization of dopamine in an aqueous solution. The catechol and amino of polydopamine could bind various metal ions and in situ reduce some noble metal ions. Herein, a facile approach, which takes advantage of the propeties of dopamine, was developed to deposit copper layers on alumina ceramic powders, ultra-light hollow glass microspheres and PEEK plastic sheets. The samples were dispersed or immersed in an aqueous dopamine solution to obtain polydopamine coatings on the surfaces. Silver ions in the silver nitrate solution were adsorbed and in situ reduced into silver nanoparticles by polydopamine. Silver nanoparticles served as catalytic seeds to catalyze the further electroless copper plating. The surface morphologies and chemical compositions of the samples were characterized by SEM, FTIR and EDS. XRD was used to investigate the crystalline structures. The results shows:(1) The polymerization process of dopamine was effectively influenced by the reaction time, dopamine concentration, oxygen concentration and oxidants. In order to obtain the integrated and even polydopamine layer, reaction with 2g/L dopamine solution(pH=8.5) for 24 h under ambient air atmosphere is proper. Silver nanoparticles improved the reaction activity of copper ions, which led a faster and more reliable plating process compared with that without activation. The obtained compact and continuous copper layer showed strong adhesion strength on the substrate surface after electroless copper plating. The as-prepared alumina/Cu microspheres were successfully bonded with octadecanethiol on the copper surfaces, which resulted in great effect against water penetration.(2) More lightweight hollow glass microspheres were successfully deposited with continuous and compact copper layers using the improved silver-activated approach.(3) The PEEK surface was coarsened by the method of non-solvent induced phase separation(NIPS) to obtain a larger number of microscopic interconnected holes. After immersing into the concentrated H2SO4 for 8min, the sizes of the holes were uniform and the swelling layer was 28.5μm. The polydopamine-coated PEEK showed rougher surface and better hydrophilic performance. Silver nanoparticles, serving as catalytic seeds, effectively catalyzed the electroless copper plating to deposit continuous and compact copper layers on the PEEK surfaces. The thickness of the copper layer increased with the increase of deposition time. When the deposition time was 60 min, the thickness of copper layer reached 2.9μm. The copper layers still firmly adhered to the substrate after the scotch-tape test, indicating the adhesive strength reached the highest scale(5B).Compared with the traditional electroless plating, this approach is facile, environment-friendly and low-cost. More importantly, the material-independent deposition of polydopamine makes it possible to deposit copper layers on other materials.