New insights in polydopamine formation via surface adsorption

Abstract

Polydopamine is a biomimetic self-adherent polymer, which can be easily deposited on a wide variety of materials. Despite the rapidly increasing interest in polydopamine-based coatings, the polymerization mechanism and the key intermediate species formed during the deposition process are still controversial. Herein, we report a systematic investigation of polydopamine formation on halloysite nanotubes; the negative charge and high surface area of halloysite nanotubes favour the capture of intermediates that are involved in polydopamine formation and decelerate the kinetics of the process, to unravel the various polymerization steps. Data from X-ray photoelectron and solid-state nuclear magnetic resonance spectroscopies demonstrate that in the initial stage of polydopamine deposition, oxidative coupling reaction of the dopaminechrome molecules is the main reaction pathway that leads to formation of polycatecholamine oligomers as an intermediate and the post cyclization of the linear oligomers occurs subsequently. Furthermore, TRIS molecules are incorporated into the initially formed oligomers.

Control of Intermolecular Interactions toward the Production of Free-Standing Interfacial Polydopamine Films

“…This is further confirmed by the analysis of N 1s high-resolution spectra of the films since the primary-amine part of the spectrum (N–C) is less significant for the DA/Cu 1:3 sample. A very recent study showed that primary amine contribution decreases with the oxidation time; thus, the decreased level indicates a higher oxidation level . Simultaneously, secondary amine abundance in the DA oxidation products indicates the elevated intramolecular cyclization rate. , Therefore, the effect of the Cu 2+ ions appears in both intermolecular and intramolecular interactions.…”

“…A very recent study showed that primary amine contribution decreases with the oxidation time; thus, the decreased level indicates a higher oxidation level. 55 Simultaneously, secondary amine abundance in the DA oxidation products indicates the elevated intramolecular cyclization rate. 56,57 Therefore, the effect of the Cu 2+ ions appears in both intermolecular and intramolecular interactions.…”

Effect of Codeposition of Polydopamine with Polyethylenimine or Poly(ethylene glycol) Coatings on Silver Nanoparticle Synthesis

“…Codeposition involves the blending of dopamine with another component to form a copolymer that is deposited on the surface of the substrate. The components can be synthetic polymers, biomolecules, small organic molecules, or nanomaterials. − Depending on the molecular structure of the component, it forms various interactions with dopamine. The component imparts new properties to the coating on the basis of its characteristics.…”

Dihydroxy Indole-free Poly(catecholamine) for Smooth Surface Coating with Amine Functionality

“…Although the dopamine monomer consists of catechol and ethylamine, catecholamine is not the only building block of PDA. Dopamine monomer possesses several reactive sites (amine, benzene, or hydroxy), which are electrophiles or nucleophiles, respectively, and thus are prone to create various building blocks such as catecholamine, 5,6-dihydroxy indole (DHI), and dopamine quinone during self-polymerization . Among these components, catecholamine plays a crucial role in adhesion, whereas DHI interferes with adherence. , Although DHI provides a cohesive behavior by promoting intermolecular π–π interaction, cation−π interactions through abundant π-electrons, as well as covalent crosslinking at its 2-position, an abundance of DHIs decreases the adhesion behavior of PDA .…”