Co-deposition Kinetics of Polydopamine/Polyethyleneimine Coatings: Effects of Solution Composition and Substrate Surface

Abstract

Polydopamine-based chemistry has been employed for various surface modifications attributed to the advantages of universality, versatility, and simplicity. Co-deposition of polydopamine (PDA) with polyethyleneimine (PEI) has then been proposed to realize one-step fabrication of functional coatings with improved morphology uniformity, surface hydrophilicity, and chemical stability. Herein, we report the co-deposition kinetics related to the solution composition with different dopamine/PEI ratios, PEI molecular weights, dopamine/PEI concentrations, and the substrate surface with varying chemistry and wettability. The addition of PEI to dopamine solution suppresses the precipitation of PDA aggregates, resulting in an expanded time window of steady co-deposition compared with that of PDA deposition. Low-molecular-weight PEI at low concentration accelerates the co-deposition process, while high-molecular-weight PEI and high concentration of either PEI or dopamine/PEI are detrimental to the co-deposition efficiency. Meanwhile, the surface morphology and chemical composition of the co-deposition coatings can be regulated by the solution conditions during co-deposition. Moreover, obvious deviations in the co-deposition rate and the amount of substrates bearing various functional groups, such as alkyl, phenyl, hydroxyl, and carboxyl, are revealed, which are quite different from PDA deposition. The initial adsorption rates further reflect the change in interactions between the aggregates and these substrates caused by PEI, which follows the sequence of carboxyl > hydroxyl > alkyl > phenyl. These results provide deep insights into the PDA/PEI co-deposition process on various substrates.

Surface modification of boron nitride by bio‐inspired polydopamine and different chain length polyethylenimine co‐depositing

“…The N1s feature can be deconvoluted into two peaks at 398.2 and 398.6 eV, which is consistent with B─N and C─N bonds (Figure B) . In the C1s XPS spectra of BN/PDA sample, there are four carbon components with binding energies at 284.7, 286.2, 286.8, and 287.5 eV, which correspond to the C─C, C─O, C─N, and C═O components, respectively . While in Figure C1, a new peak corresponding to the π–π* shake‐up peak (approximately 290.9 eV) appeared, indicating the conjugated aromatic structure of the PDA polymer .…”

Surface Zwitterionization of Expanded Poly(tetrafluoroethylene) via Dopamine-Assisted Consecutive Immersion Coating

“…In the first coating, dopamine self-polymerizes and randomly reacts with amine moieties in PEI to form a co-deposited layer of PDA/ PEI on the membrane surface. 38 As mentioned previously, the stoichiometry of this reaction, in terms of moles of reactive amine groups, is unaffected by PEI molecular weight. In the second coating, the epoxy rings of the PGS are attacked and opened by the unreacted nucleophilic amine groups in PEI (mostly secondary and tertiary amines not participating in the Schiff base and Michael addition reactions earlier), forming a covalently linked second layer.…”

“…This in effect "buries" the adhesive groups of PDA within the conjugates, causing stabilization in the aqueous phase and resulting in an overall decrease in the amount of PDA/PEI conjugates deposited. 38 This is reinforced by observations from succeeding physicochemical characterizations.…”

Development of Stimulus‐Responsive Degradable Film via Codeposition of Dopamine and Cystamine

“…Although the detailed mechanism of pD film formation is still elusive and under debate, the general agreement is that oxidized dopamine forms 5,6‐dihydroxyindole (DHI) and is further assembled into various types of oligomers including DHI 2 dimers, (dopamine) 2 /DHI trimers, and dopamine–DHI 2 trimers, whose π–π stacking, hydrogen bonding, and covalent interactions form aggregates that are deposited on the surfaces, forming a universal pD film . The prolonged reaction time forms larger aggregates, which tend to be precipitated from the solution rather than being deposited on the surfaces . We postulated that the initial ratio of dopamine/cystamine in the solution affected the kinetics of aggregate formation.…”

“…[14] The prolonged reaction time forms larger aggregates, which tend to be precipitated from the solution rather than being deposited on the surfaces. [15] We postulated that the initial ratio of dopamine/ cystamine in the solution affected the kinetics of aggregate formation. A suitable amount of cystamine would alleviate fast formation of indoles, because amine groups from cystamine would compete with those from the oxidized dopamine.…”