Ion‐Specific Oil Repellency of Polyelectrolyte Multilayers in Water: Molecular Insights into the Hydrophilicity of Charged Surfaces

Liu, Xiaokong; Leng, Chuan; Yu, Li; He, Ke; Brown, Lauren Joan; Chen, Zhan; Cho, Jinhan; Wang, Dayang

doi:10.1002/anie.201411992

Cited by 74 publications

(75 citation statements)

References 23 publications

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“…37 The Si-OH and NanoZnO surfaces show excellent underwater oil repellency as well (Figure 1b and Figure S4), which is ascribed to the hydration of hydroxyl groups for the former 37 and the combination role of surface roughness and ZnO hydrophilicity for the latter 31,32,38 . In contrast, although PEG is also a widely used material for anti-biofouling surfaces, 14 the surface of PEG brushes obtained via self-assembly of thiol-terminated PEG onto gold substrate (Au-PEG) can be easily contaminated by oil in water (Scheme S3 and Figure S5), despite it is underwater oleophobic with an OCA-W of 130.0° (Figure 1b).…”

Section: Resultsmentioning

confidence: 95%

“…In contrast, the PDDA/PSS surface is hydrophobic in oil with WCA-O of 100° (Figure 1a and 1d), which is ascribed to the molecular configuration change of the benzenesulfonate groups at interface when immersing in oil. 37 For the Nano-ZnO surface immersed in oil, water droplets are completely repelled with WCA-O above 165° (Figure 1a and 1f), because ZnO nanostructures can effectively trap oil and thus repel water, 39 which is similar to the repellence of water or oil in air by textured surfaces with low surface energy. [40][41][42][43] Although the Si-OH surface is shown to be hydrophilic in oil, its WCA-O (ca.…”

Section: Resultsmentioning

confidence: 97%

“…(ii) PDDA/PSS surfaces were prepared by alternate deposition of PDDA and PSS on Piranha solution cleaned Si substrates for 4 cycles. 37 In the PDDA or PSS solution, the concentration of PDDA or PSS is 1.0 mg/mL and the concentration of NaCl is 1.0 M. (iii) Nano-ZnO surfaces were obtained by growing ZnO nanostructures on steel plates (25 mm * 18 mm) by using the protocol reported in the literature. 34 Typically, the stainless steel plates were first incubated in HNO 3 solution (4 M) at 60 °C for 4h, followed by sonication with water, 2-propanol and ethanol for 10 min, respectively, and finally they were dried by N 2 flow.…”

Section: Preparation Of Pmpcmentioning

confidence: 99%

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Cleaning of Oil Fouling with Water Enabled by Zwitterionic Polyelectrolyte Coatings: Overcoming the Imperative Challenge of Oil–Water Separation Membranes

et al. 2015

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Herein we report a self-cleaning coating derived from zwitterionic poly(2-methacryloyloxylethyl phosphorylcholine) (PMPC) brushes grafted on a solid substrate. The PMPC surface not only exhibits complete oil repellency in a water-wetted state (i.e., underwater superoleophobicity), but also allows effective cleaning of oil fouled on dry surfaces by water alone. The PMPC surface was compared with typical underwater superoleophobic surfaces realized with the aid of surface roughening by applying hydrophilic nanostructures and those realized by applying smooth hydrophilic polyelectrolyte multilayers. We show that underwater superoleophobicity of a surface is not sufficient to enable water to clean up oil fouling on a dry surface, because the latter circumstance demands the surface to be able to strongly bond water not only in its pristine state but also in an oil-wetted state. The PMPC surface is unique with its described self-cleaning performance because the zwitterionic phosphorylcholine groups exhibit exceptional binding affinity to water even when they are already wetted by oil. Further, we show that applying this PMPC coating onto steel meshes produces oil-water separation membranes that are resilient to oil contamination with simply water rinsing. Consequently, we provide an effective solution to the oil contamination issue on the oil-water separation membranes, which is an imperative challenge in this field. Thanks to the self-cleaning effect of the PMPC surface, PMPC-coated steel meshes can not only separate oil from oil-water mixtures in a water-wetted state, but also can lift oil out from oil-water mixtures even in a dry state, which is a very promising technology for practical oil-spill remediation. In contrast, we show that oil contamination on conventional hydrophilic oil-water separation membranes would permanently induce the loss of oil-water separation function, and thus they have to be always used in a completely water-wetted state, which significantly restricts their application in practice.

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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 97%

Section: Preparation Of Pmpcmentioning

confidence: 99%

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Cleaning of Oil Fouling with Water Enabled by Zwitterionic Polyelectrolyte Coatings: Overcoming the Imperative Challenge of Oil–Water Separation Membranes

et al. 2015

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“…For example, Wang et al reported polyelectrolyte multilayers (PEMs) that were fabricated by alternative deposition of polydiallyldimethylammonium chloride (PDDA) and poly(styrene sulfonate) (PSS) respectively. The PEMs showed ion‐specific oil repellency in water . Shiratori et al prepared antifibrinogen, antireflective, and antifogging surfaces by alternative deposition of PAH−PVA−PAA mixture (as the cationic solution) with PVA−PAA mixture (as the anionic solution) .…”

Section: Surface Modification Of the Micro‐/nanostructurementioning

confidence: 99%

Micro‐/Nanostructured Interface for Liquid Manipulation and Its Applications

Duan

Zheng

Zhao

et al. 2019

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Understanding the relationship between liquid manipulation and micro‐/nanostructured interfaces has gained much attention due to the wide potential applications in many fields, such as chemical and biomedical assays, environmental protection, industry, and even daily life. Much work has been done to construct various materials with interfacial liquid manipulation abilities, leading to a range of interesting applications. Herein, different fabrication methods from the top‐down approach to the bottom‐up approach and subsequent surface modifications of micro‐/nanostructured interfaces are first introduced. Then, interactions between the surface and liquid, including liquid wetting, liquid transportation, and a number of corresponding models, together with the definition of hydrophilic/hydrophobic, oleophilic/olephobic, the definition and mechanism of superwetting, including superhydrophobicity, superhydrophilicity, and superoleophobicity, are presented. The micro‐/nanostructured interface, with major applications in self‐cleaning, antifogging, anti‐icing, anticorrosion, drag‐reduction, oil–water separation, water collection, droplet (micro)array, and surface‐directed liquid transport, is summarized, and the mechanisms underlying each application are discussed. Finally, the remaining challenges and future perspectives in this area are included.

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“…[1] Since their ionic groups can superiorly bind water molecules by strong electrostatically induced hydration, polyelectrolytes can be easily wetted by water in air, exhibiting outstanding hydrophilicity. [1a, 2] These tightly bound water molecules render the polyelectrolyte chains highly swelled in water, [2,3] and are believed to be the major mechanism for their promising applications such as underwater oil repellency, [4] antifouling, [1b, 5] oil/water separation, [6] and lubrication. [7] Of all polyelectrolytes,t he zwitterionic ones exhibit excellent hydrophilicity and hydration strength by integrating both positive and negative ionic groups.…”

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confidence: 99%

Long‐Range Hydrophilic Attraction between Water and Polyelectrolyte Surfaces in Oil

et al. 2016

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The outstanding water wettability and the capability of polyelectrolyte surfaces to spontaneously clean oil fouling are determined by their wetting mechanism in the surrounding medium. Here, we have quantified the nanomechanics between three types of polyelectrolyte surfaces (i.e. zwitterionic, cationic, and anionic) and water or oil drops using an atomic force microscope (AFM) drop probe technique, and elucidated the intrinsic wetting mechanisms of the polyelectrolyte surfaces in oil and water media. The measured forces between oil drops and polyelectrolyte surfaces in water can be described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Surprisingly, strong long-range attraction was discovered between polyelectrolyte surfaces and water drops in oil, and the strongest interaction was measured for the polyzwitterion. This unexpected long-range "hydrophilic" attraction in oil could be attributed to a strong dipolar interaction because of the large dipole moment of the polyelectrolytes. Our results provide new nanomechanical insights into the development of novel polyelectrolyte-based materials and coatings for a wide range of engineering, bioengineering, and environmental applications.

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Ion‐Specific Oil Repellency of Polyelectrolyte Multilayers in Water: Molecular Insights into the Hydrophilicity of Charged Surfaces

Cited by 74 publications

References 23 publications

Cleaning of Oil Fouling with Water Enabled by Zwitterionic Polyelectrolyte Coatings: Overcoming the Imperative Challenge of Oil–Water Separation Membranes

Cleaning of Oil Fouling with Water Enabled by Zwitterionic Polyelectrolyte Coatings: Overcoming the Imperative Challenge of Oil–Water Separation Membranes

Micro‐/Nanostructured Interface for Liquid Manipulation and Its Applications

Long‐Range Hydrophilic Attraction between Water and Polyelectrolyte Surfaces in Oil

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