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Enhanced under water superoleophobicity by micro/nano topography and hydrophilic polymer brushes for high efficiency oil-water emulsion separation

Periodic Reporting for period 1 - HYDRA (Enhanced under water superoleophobicity by micro/nano topography and hydrophilic polymer brushes for high efficiency oil-water emulsion separation)

Reporting period: 2019-01-07 to 2021-01-06

Superhydrophilic-underwater superoleophobic membrane is a kind of functional separation membranes based on specialwettability, with very promising application prospect in oil/water separation. The stability of the material is the key factor in its performance. This proposal aims to develop stable membranes with superhydrophilicity-underwater superoleophobicity design, by combining synergistically the stupendous hydrated polymer brushes and anisotropic micro-/nano-structures on a surface. Our results aim to reveal the relationships between the molecular brush structure, anisotropic micro-/nano-structure on the surface, and wettability in the oil-water-solid three phase system, illustrating the nature of science of wetting transition and transition suppression, understanding the mechanism of superhydrophilic-underwater superoleophobic surfaces under pressure in multiple phase systems, and ultimately establishing the design strategy for effective membranes for oil-water separation important in many applications of significant economic and societal impact.
1.Overview of the results
1) The effects of micro-nanostructure on the stability and mechanism of underwater superoleophobicity
A micro-nano composite surface was prepared through a simple method of self-assembly of SiO2 NPs with hydrophilic polymer brushes. The effects of surface roughness on static and dynamic wettability were studied to explore the stability and mechanism of underwater superoleophobicity. These surfaces are oleophilic in the air, and the oil contact angle gradually decreases with the increase of roughness. While the surfaces show superoleophobicity underwater, and the underwater oil contact angles gradually increase with the increase of roughness. The rough micro-nanostructure can trap the water and form a stable water lay which can restrain the wetting of oil.
2) The effects of Polymer brushes on the stability and mechanism of underwater superoleophobicity under pressure
The mechanism of wetting behavior of superhydrophilic coating with different function groups were studied to guide to design a stable self-cleaning surface. The chemical composition, surface roughness, static and dynamic wettability, underwater oil adhesive force, and swelling degree of the coatings are studied to explore their oil dewetting mechanism. The results indicate that the wettability of the coating to water and oil is the key factor to determine the self-cleaning performance. The anionic coating shows the best self-cleaning performance because of its extremely strong hydration ability.
3) Mixed liposomes containing gram-positive bacteria lipids: Lipoteichoic acid (LTA) induced structural changes
Lipoteichoic acid (LTA), a surface associated polymer amphiphile tethered directly to the Gram-positive bacterial cytoplasmic membrane, is a key structural and functional membrane component. We have investigated structural changes in mixed liposomes mimicking the lipid composition of Gram-positive bacteria membranes. SANS and DLS measurements indicated formation of mixed unilamellar vesicles, presumably stabilized by the negatively charged LTA polyphosphates. At 80°C, SANS analyses showed the formation of larger vesicles with thinner shells. The results are discussed in light of the steric and electrostatic interactions of the bulky LTA molecules with increased chain fluidity at the higher temperature, which affect the molecular packing and interactions, and thus depend on the LTA composition, in the membrane.
4) Lipopolysaccharide (LPS) is a key structural component of the outer membrane of gram-negative bacteria. To develop effective and alternative antibacterial agents, it is crucial to understand the structure of, and fundamental interactions at, the bacterial cell wall. Here, the effects of Na+, Ca2+, and La3+, as well as LPS carbohydrate head group length on the structure, size and electrostatic properties of LPS aggregates at near physiological conditions are studied. The results show LPS-Ra forms elliptical and elliptical cylinder micelles with diameter around 10nm without any cations. The micelles transform to monolayer and multilayer vesicles with the increase of CaCl2 solution. According to the results, the effects of cations on the morphological transformation of LPS-Ra aggregates can be ascribe to the electrostatic screening of ion effects of Na+ and crosslink of ion-specific effect of Ca2+, respectively.
2. Exploitation and dissemination
1) As the co-author, the results from this fellowship have produced one high-quality articles in international journal Colloids and Surfaces B: Biointerfaces (Gold Open access) we have 2 more manuscripts under preparation, which will give high visibility to our novel concept to inspire the global chemical community.
2) The fellow attended The 33rd Conference of the European Colloid and Interface Society (ECIS) (invited poster, University of Leuven, Belgium, September, 2019). In the dissemination activities, the projects were presented to outstanding young chemists from different countries, and European Union has been acknowledged following the rules detailed in the EU Horizon-2020 portal. The fellow has attended the M4 Colloids Symposium in the year 2019. During this meeting held in the University of Bath, the fellow introduced his projects to the most influential academics, thus enabling the fellow to forge new important network links.
3) Finally, the fellow has contributed to organize 2019 Future European Researchers’ Night at Bristol, where many scientists from university had the opportunity to showcase the popular science to the general public. The result has been a fantastic day of science and discussion with young students and families.
1) Impact on the researcher's career: the fellow has gained a lot of research experiences during the implementation of the projects. He has also established his research network with many outstanding young chemists in the host group, and has established his reputation in the fields of polymer chemistry and colloid physical chemistry through publishing the results in high-impact journals and presenting his work in international conferences. Completing independent projects while supervising younger colleagues or collaborating with other chemists during this fellowship greatly enhanced his management and communication skills. As a result, the fellow obtained an independent research academic position in Ningbo Institute of Materials Technology and Engineering (Chinese Academy of Sciences), a prestigious research institution in China.
2) Impact on the academic community: the chemistry detailed in the modified action has resulted in one publication in high-impact international journal with two manuscripts under preparation, which tremendously impacted academia, triggering growing interest about the topics discovered, including high performance membrane, antifouling, and antibacterial.
3) Impact on the industry: Superhydrophilic-underwater superoleophobic membrane is a kind of functional separation membranes based on special wettability, has a fairly bright application prospect in oil/water separation. The new strategy of the combination of hydrophilic polymer brushes and micro-nano structures to construct a stable underwater superoleophobic system opened new sight to build a high-performance membrane. The discoveries are expected to significantly impact the membrane industry.
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