Insights into the Aggregation/Deposition and Structure of a Polydopamine Film

Abstract

Surface-adherent polydopamine (PDA) films as multifunctional coatings can be easily deposited onto a wide range of materials through dopamine self-polymerization. However, a lack of in-depth understanding of PDA aggregation and deposition processes and definite structure elucidation of PDA make it challenging to tailor the surface characteristic and functionality of the PDA films. Herein, we demonstrate that the surface characteristics of the PDA films can be readily tuned by controlling the competitive interplay between PDA aggregation in solution and deposition on the substrate. Moreover, a structural investigation of the PDA films using analytical tools such as X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) allows us to propose a new structure model for the PDA building block. The (DHI)2/PCA trimer complex, which consists of two 5,6-dihydroxyindole (DHI) units and one pyrrolecarboxylic acid (PCA) moiety, is definitely identified as a primary building block of PDA, and its formation is steered by covalent interactions in the initial stages of polymerization. In latter stages, the (DHI)2/PCA trimer complexes are further linked primarily through noncovalent interactions to build up the supramolecular structure of PDA. This study provides new insights into the mechanisms of PDA buildup.

Investigation of the chemical structure and formation mechanism of polydopamine from self‐assembly of dopamine by liquid chromatography/mass spectrometry coupled with isotope‐labelling techniques

“…Analysis of the extraction‐cleaned polyDp material via TOF‐SIMS, an analytical technique that has been used extensively to analyze the molecular composition at the surface of solid materials, revealed a strong signal at m/z 149.02 (Figure ), which signified the radical cation of dopaminechrome, and the signal for unmodified Dp. The analysis again revealed dopaminechrome was the major monomer unit.…”

“…Previous studies have demonstrated that polyDp can be a mixture of covalently bonded polymers and non‐covalent supramolecular aggregates with low solubility in most protic and aprotic solvents . It is likely that the covalent cross‐linking and inter‐strand cross‐linking between the covalent polymers ( 4 ) and the non‐covalent monomers ( 5 and 7 ) stabilize both the non‐covalent oligomeric clusters and the covalently bonded polymers to prevent them from solvation …”

Palladium on Polydopamine: Its True Potential in Catalytic Transfer Hydrogenations and Heck Coupling Reactions

“…The polymerization of DA has been investigated extensively regarding mechanism, conditions, additives, and polymer structure . Generally, the polymeric material forms under basic aqueous conditions in the presence of O 2 in water or water/alcohol solvent mixtures .…”

CuSO4/H2O2‐Induced Rapid Deposition of Polydopamine Coatings with High Uniformity and Enhanced Stability

“…[17] Figure 2shows the results of PDAd eposited on as ilicon wafer using CuSO 4 /H 2 O 2 as at rigger.A FM images demonstrate the PDAc oatings are composed of many nanoparticles.The average surface roughness (R q )i ncreases from 0.958 nm to 1.594 nm for those coatings deposited by 20 min and 40 min, respectively.B y contrast, R q increases from 1.27 nm to 8.88 nm when PDA coatings are deposited above room temperature (60 8 8C) and under vigorous stirring for 30 min. [17] Figure 2shows the results of PDAd eposited on as ilicon wafer using CuSO 4 /H 2 O 2 as at rigger.A FM images demonstrate the PDAc oatings are composed of many nanoparticles.The average surface roughness (R q )i ncreases from 0.958 nm to 1.594 nm for those coatings deposited by 20 min and 40 min, respectively.B y contrast, R q increases from 1.27 nm to 8.88 nm when PDA coatings are deposited above room temperature (60 8 8C) and under vigorous stirring for 30 min.…”