Issue 42, 2019

Unravelling the polydopamine mystery: is the end in sight?

Abstract

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?

Supplementary files

Article information

Article type
Paper
Submitted
11 Sep 2019
Accepted
07 Oct 2019
First published
08 Oct 2019

Polym. Chem., 2019,10, 5771-5777

Unravelling the polydopamine mystery: is the end in sight?

Q. Lyu, N. Hsueh and C. L. L. Chai, Polym. Chem., 2019, 10, 5771 DOI: 10.1039/C9PY01372E

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