Polydopamine and Its Derivative Materials: Synthesis and Promising Applications in Energy, Environmental, and Biomedical Fields

Recent development of polymer electrolyte membranes for fuel cells.

Herein we propose a new structure for poly(dopamine), a synthetic eumelanin that has found broad utility as an antifouling agent. Commercially available 3-hydroxytyramine hydrochloride (dopamine HCl) was polymerized under aerobic, aqueous conditions using tris(hydroxymethyl)aminomethane (TRIS) as a basic polymerization initiator, affording a darkly colored powder product upon isolation. The polymer was analyzed using a variety of solid state spectroscopic and crystallographic techniques. Collectively, the data showed that in contrast to previously proposed models, poly(dopamine) is not a covalent polymer but instead a supramolecular aggregate of monomers (consisting primarily of 5,6-dihydroxyindoline and its dione derivative) that are held together through a combination of charge transfer, π-stacking, and hydrogen bonding interactions.

Elucidating the Structure of Poly(dopamine)

Polydopamine (PDA) formed by the oxidation of dopamine is an important polymer, in particular, for coating various surfaces. It is composed of dihydroxyindole, indoledione, and dopamine units, which are assumed to be covalently linked. Although PDA has been applied in a manifold way, its structure is still under discussion. Similarities have been observed in melanins/eumelanins as naturally occurring, deeply colored polymer pigments derived from l-DOPA. Recently, an alternative structure was proposed for PDA wherein dihydroxyindoline, indolinedione, and eventually dopamine units are not covalently linked to each other but are held together by hydrogen bonding between oxygen atoms or π stacking. In this study, we show that this structural proposal is very unlikely to occur taking into account unambiguous results obtained by different analytical methods, among them 13C CPPI MAS NMR (cross-polarization polarization–inversion magic angle spinning NMR), 1H MAS NMR (magic angle spinning NMR), and ES-HRMS (elect...

Structure of polydopamine: a never-ending story?

Overview on the application of direct methanol fuel cell (DMFC) for portable electronic devices

Design and fabrication of hierarchically structured membranes with high proton conductivity is crucial to many energy-relevant applications including proton exchange membrane fuel cell (PEMFC). Here, a series of imidazole microcapsules (IMCs) with tunable imidazole group loading, shell thickness, and lumen size are synthesized and incorporated into a sulfonated poly(ether ether ketone) (SPEEK) matrix to prepare composite membranes. The IMCs play two roles: i) Improving water retention properties of the membrane. The IMCs, similar to the vacuoles in plant cells, can render membrane a stable water environment. The lumen of the IMCs acts as a water reservoir and the shell of IMCs can manipulate water release. ii) They form anhydrous proton transfer pathways and low energy barrier pathways for proton hopping, imparting an enhanced proton transfer via either a vehicle mechanism or Grotthuss mechanism. In particular, at the relative humidity (RH) as low as 20%, the composite membrane exhibits an ultralow proton conductivity decline and the proton conductivity is one to two orders of magnitude higher than that of SPEEK control membrane. The enhanced proton conductivity affords the composite membrane an elevated peak power density from 69.5 to 104.5 mW cm−2 in a single cell. Moreover, the application potential of the composite membrane for CO2 capture is explored.

Enhancement of Proton Conduction at Low Humidity by Incorporating Imidazole Microcapsules into Polymer Electrolyte Membranes

Surface-modified Y zeolite-filled chitosan membrane for direct methanol fuel cell

Effect of zeolites on chitosan/zeolite hybrid membranes for direct methanol fuel cell

The development of new functional materials requires cutting-edge technologies for incorporating different functional materials without reducing their functionality. Microencapsulation is a method to encapsulate different functional materials at nano- and micro-scales, which can provide the necessary protection for the encapsulated materials. In this review, microencapsulation is categorized into chemical, physical, physico-chemical and microfluidic methods. The focus of this review is to describe these four categories in detail by elaborating their various microencapsulation methods and mechanisms. This review further discusses the key features and potential applications of each method. Through this review, the readers could be aware of many aspects of this field from the fabrication processes, to the main properties, and to the applications of microcapsules.

Jingtao Wang

Papers

Enhancement of Proton Conduction at Low Humidity by Incorporating Imidazole Microcapsules into Polymer Electrolyte Membranes

Surface-modified Y zeolite-filled chitosan membrane for direct methanol fuel cell

Effect of zeolites on chitosan/zeolite hybrid membranes for direct methanol fuel cell

Fabrication and application of complex microcapsules: a review

Bioinspired fabrication of high performance composite membranes with ultrathin defect-free skin layer