Polydopamine Films from the Forgotten Air/Water Interface

Abstract

The formation of polydopamine under mild oxidation conditions from dopamine solutions with mechanical agitation leads to the formation of films that can functionalize all kinds of materials. In the absence of stirring of the solution, we report the formation of polydopamine films at the air/water interface (PDA A/W) and suggest that it arises from an homogeneous nucleation process. These films grow two times faster than in solution and can be deposited on hydrophilic or hydrophobic substrates by the Langmuir-Schaeffer technique. Thanks to this new method, porous and hydrophobic materials like polytetrafluoroethylene (PTFE) membranes can be completely covered with a 35 nm thick PDA A/W film after only 3h of reaction. Finally the oxidation of a monomer followed by a polymerization in water is not exclusive to polydopamine since we also transferred polyaniline functional films from the air/water interface to solid substrates. These findings suggest that self-assembly from a solution containing hydrophilic monomers undergoing a chemical transformation (here oxidation and oligomerization) could be a general method to produce films at the liquid/air interface.

Polydopamine deposition at fluid interfaces

“…After a critical reaction time these films could be withdrawn from the water/air interface using the horizontal Langmuir–Schaeffer method at a slow withdrawal rate of a few micrometres per second. After film removal, the water/air interface was progressively recolonized by a PDA coating, showing the intrinsic self‐healing properties of PDA at such a fluid interface . The deposition of PDA at the solid/liquid interfaces as well as at the water/air interface is similar to the deposition process of polyaniline suggesting a similar deposition mechanism (Fig.…”

Surface engineering of polymer membranes via mussel-inspired chemistry

“…Both the flux and rejection were promoted due to the thinner and denser skin layer derived from the reactions between PEI and PDA as we mentioned in Section 3.1. Anyway, PDA is still an ideal candidate for nanofiltration skin layer because of its intrinsic rigid structure, which can enhance the membrane stability [167], and PDA-based free-standing films have been reported by several groups recently [168][169][170].…”

Microwave‐Accelerated Rapid, Chemical Oxidant‐Free, Material‐Independent Surface Chemistry of Poly(dopamine)

“…Previously, fast pDA formation at the air-contacting interface (i.e., air/water interface) was observed. [37][38][39] When the solution temperature www.small-journal.com is gradually increased, the amount of dissolved oxygen is decreased because gas solubility has an inverse relationship with temperature. Below ≈60 °C, the temperature-induced acceleration of the coating reaction is dominant, compensating for the decreased amount of oxygen catalyst (i.e., dissolved oxygen).…”