A Universal Strategy for the Preparation of Dual Superlyophobic Surfaces in Oil-Water Systems

Mingming Wu; Guogui Shi; Weimin Liu; Yifei Long; Peng Mu; Jian Li

doi:10.1021/acsami.1c02187

A Universal Strategy for the Preparation of Dual Superlyophobic Surfaces in Oil-Water Systems

ACS Appl Mater Interfaces. 2021 Mar 31;13(12):14759-14767. doi: 10.1021/acsami.1c02187. Epub 2021 Mar 22.

Authors

Mingming Wu¹, Guogui Shi¹, Weimin Liu¹, Yifei Long¹, Peng Mu¹, Jian Li^{1

2}

Affiliations

¹ Key Laboratory of Eco-Functional Polymer Materials of the Ministry of Education, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. China.
² School of Materials Science and Hydrogen Energy, Foshan University, Foshan 528000, P. R. China.

PMID: 33749236
DOI: 10.1021/acsami.1c02187

Abstract

There are some methods to prepare superwetting surfaces with underwater superoleophobicity (UWSOB) or underoil superhydrophobicity (UOSHB), but it is still thorny to put forward a universal strategy for constructing dual superlyophobic surfaces in oil-water systems due to a thermodynamic contradiction. Herein, a universal strategy was proposed to prepare the dual superlyophobic surfaces in oil-water systems only via delicately controlling surface chemistry, that is, adjusting the ratios of superhydrophilic and superhydrophobic counterparts in the spray solution. Three types of materials, attapulgite (APT), TiO₂, and loess, were chosen to prepare a diverse series of mixed coatings (mass gradient of superhydrophobic counterparts from 0 to 100 wt %). With the proportion of each superhydrophobic counterpart increasing, the underwater oil contact angle (θ_o/w^*) of each mixed coating slightly decreased but still was more than 150°, that is, UWSOB. In contrast, the underoil water contact angle (θ_w/o^*) was significantly improved, realizing the transformation from UOHL (or UOHB) to UOSHB. More importantly, the respective mass ratios of superhydrophobic counterparts in the resulting mixed coatings of APT, TiO₂, and loess were finally determined to be 0.3, 0.4, and 0.2, respectively. Taking APT as a model, a train of mixed APT coatings with different superhydrophobic components were systematically characterized and analyzed. Finally, the prepared superlyophobic separation mesh in oil-water systems was applied to the separation of various surfactant-stabilized oil-water emulsions. We envision that this universal strategy we proposed will show a significant application potential in addressing scientific and technological challenges in the field of interfacial chemistry such as oil-water separation, microfluidics, microdroplet manipulation, antifogging/icing, cell engineering, drag reduction, and so forth.

Keywords: oil−water emulsion separation; thermodynamic contradiction; underoil superhydrophobicity (UOSHB); underwater superoleophobicity (UWSOB); universal strategy.