Amine-Triggered Dopamine Polymerization: From Aqueous Solution to Organic Solvents

Dopamine (DA) polymerization has received significant attention in many fields, however, almost all of the works are limited to aqueous solution and hamper its wide application. This paper reports that amines can trigger DA polymerization by capturing the H⁺ from DA hydrochloride and intermediates to accelerate the generation of radical species in water or organic solvents. Increasing concentration and decreasing pKb of amines cause the reaction equilibrium to shift toward the product polydopamine (PDA). Water-soluble and easily-removable Na₂ SO₄ nanowires and NaCl cubes can be used as templates to prepare different morphologies of hollow PDA structures by DA polymerization in ethanol solution. The carbonization production of PDA nanotubes at 900 °C (PDNC-900) is obtained and demonstrates electrochemical activity in the oxygen reduction reaction that is comparable to that of Pt/C.