On June 9, the research work entitled "Spontaneous water-on-water spreading of polyelectrolyte membranes inspired by skin formation" was published online at Nature Communications (DOI: https://doi.org/10.1038/s41467-022-30973-6). This work was conducted by the research group led by Prof. Zhao Qiang from the School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology.
Stable interfaces between immiscible solvents are crucial for chemical synthesis and assembly, but interfaces between miscible solvents have been less explored. Here the authors report the spontaneous water-on-water spreading and self-assembly of polyelectrolyte membranes. An aqueous mixture solution containing poly(ethyleneimine) and poly(sodium 4-styrenesulfonate) spreads efficiently on acidic water, leading to the formation of hierarchically porous membranes. The reduced surface tension of the polyelectrolyte mixture solution drives the surface spreading, while the interfacial polyelectrolytes complexation triggered by the low pH of water mitigates water-in-water mixing. The synergy of surface tension and pH-dependent complexation represents a generic mechanism governing interfaces between miscible solvents for materials engineering, without the need for surfactants or sophisticated equipment. As a proof-of-concept, porous polyelectrolyte hybrid membranes are prepared by surface spreading, exhibiting exceptional solar thermal evaporation performance (2.8 kg/m2h) under 1-sun irradiation.
The first author is Tang Sihan, who is a postgraduate of School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology. The collaborate units include School of Materials Science and Engineering of HUST and Union Hospital, Tongji Medical College, Huazhong University of Science and Technology. This work was funded by the National Natural Science Foundation of China, National Key R&D Program and Three Gorges Laboratory Open Fund.
Link to this paper: https://www.nature.com/articles/s41467-022-30973-6