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Unravelling the polydopamine mystery: is the end in sight?

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Despite the prominence of polydopamine (PDA) in the field of polymer and materials chemistry since it was first reported by H. Lee, S. M. Dellatore, W. M. Miller and P. B. Messersmith, Science, 2007, 318, 426–430, the structure of PDA has been an unresolved and contentious issue. Current consensus favors polymers derived from the cyclized intermediate 5,6-dihydroxyindole (DHI). In this work, compelling evidence for the possible structure of PDA is shown via detailed mass spectroscopic studies using deuterium-labeled dopamine (DA) precursors. More specifically, the major component of PDA is shown to derive from dopaminochrome (DAC) and uncyclized DA components. One major intermediate, seen at m/z 402, is characterized as a combination of benzazepine + DAC + 2H-pyrrole, which has a chemical formula of C23H20N3O4. Furthermore, DAC forms stable complexes with DA, and is a key control point in the polymerization of PDA. The decay of DAC into DHI is a relatively slow process in the presence of excess DA, and plays a smaller role in PDA formation. This study shows the covalent connectivity in PDA from the starting DA monomer, and represents an important advance in elucidating the structure of PDA.

Graphical abstract: Unravelling the polydopamine mystery: is the end in sight?

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The article was received on 11 Sep 2019, accepted on 07 Oct 2019 and first published on 08 Oct 2019

Article type: Paper
DOI: 10.1039/C9PY01372E
Polym. Chem., 2019, Advance Article

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    Unravelling the polydopamine mystery: is the end in sight?

    Q. Lyu, N. Hsueh and C. L. L. Chai, Polym. Chem., 2019, Advance Article , DOI: 10.1039/C9PY01372E

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