Experimental and theoretical analysis of polymerization reaction process on the polydopamine membranes and its corrosion protection properties for 304 Stainless Steel

PDA-assisted surface modification is strongly subjected to the formation of PDA coating on the biomaterial interface caused by the oxidation reaction of dopamine (DA) in weak alkaline solution.

“PDA-assisted surface modification is strongly subjected to the formation of PDA coating on the biomaterial interface caused by the oxidation reaction of dopamine (DA) in weak alkaline solution.”

Due to the composition similar to some proteins in organism, PDA can also offer some bioprotection functions, such as photoprotection, reactive oxygen species scavenging (ROS), and metal cation sequestering.

“In addition, due to the composition similar to some proteins in organism, PDA can also offer some bioprotection functions, such as photoprotection, reactive oxygen species scavenging (ROS), and metal cation sequestering [30, 31].”

The reverse dismutation reaction occurs between 5,6-dihydroxyindole and its further oxidized intermediate (indolequinone) (C substep) finally leads to PDA (D sub-step).

“The reverse dismutation reaction occurs between 5,6-dihydroxyindole and its further oxidized intermediate (indolequinone) (C substep) finally leads to PDA (D sub-step) [31].”

Dopaminequinone is subjected to intramolecular cyclization (A substep), reversible oxidation to form dopaminechrome, and intramolecular rearrangement to lead to 5,6-dihydroxyindole (B substep).

“Dopaminequinone is subjected to intramolecular cyclization (A substep), reversible oxidation to form dopaminechrome, and intramolecular rearrangement to lead to 5,6-dihydroxyindole (B substep).”

Several mechanisms of the PDA coating layer have been developed and they all consist essentially of two steps, including the autooxidation and intramolecular rearrangement of DA monomers and polymerization of DA monomers.

“Several mechanisms of the PDA coating layer have been developed and they all consist essentially of two steps as shown in Figure 1, including the autooxidation and intramolecular rearrangement of DA monomers and polymerization of DA monomers [29, 31, 38].”

These DA based monomers and other important conditions of PDA polymerization become decisive factors to impact the formation of PDA layer.

“These DA based monomers and other important conditions of PDA polymerization become decisive factors to impact the formation of PDA layer [31, 37].”

The first step involves the occurrence of autooxidation of DA monomers where dopaminequinone is synthesized in the presence of dissolved oxygen, alkaline buffer, and adequate supply of initial dopamine monomers.

“The first step involves the occurrence of autooxidation of DA monomers where dopaminequinone is synthesized in the presence of dissolved oxygen, alkaline buffer, and adequate supply of initial dopamine monomers.”

Eumelanin is naturally formed with the L-3,4-dihydroxyphenylalanine (L-DOAP) or tyrosine as precursors.

“Eumelanin is naturally formed with the L-3,4-dihydroxyphenylalanine (L-DOAP) or tyrosine as precursors.”

The polydopamine coating layer can offer good surface properties such as high hydrophilicity, long-term corrosion resistance, and moderate physicochemical properties.

“can offer good surface properties such as high hydrophilicity, long-term corrosion resistance, and moderate physicochemical properties [31, 53, 54].”