Facile Preparation of Raspberry-Like SiO2@Polyurea Microspheres with Tunable Wettability and Their Application for Oil–Water Separation

• Published in: ACS applied materials & interfaces 2024-10, Vol.16 (42), p.57672-57686
• Main Authors: Jiang, Xubao, Zhang, Diankai, Wang, Yujun, Wang, Ruiqing, Kong, Xiang Zheng, Zhu, Xiaoli, Li, Shusheng, Gu, Xiangling
• Format: Article
• Language: English
• Subjects: Applications of Polymer, Composite, and Coating Materials
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/acsami.4c12378

Raspberry-like microspheres have been widely used as superhydrophobic materials, photonic crystals, drug carriers, etc. Nevertheless, their preparation methods, usually consisting of multiple steps, are generally time- and energy-consuming. Herein raspberry-like SiO2@polyurea microspheres (SiO2@PUM) are readily prepared via a one-step precipitation polymerization of isophorone diisocyanate in a H2O/acetone mixture with the presence of SiO2 particles. The sphere size, surface roughness, and SiO2 content of SiO2@PUM are easily adjustable by varying the experimental conditions. TEM and SEM observations reveal that the final SiO2@PUM exhibits a core–shell structure, with polyurea (PU) in the core and SiO2 particles as the shell. In the process, the SiO2 particles were initially located on the PUM surface as a monolayer. With the reaction proceeding, the monolayer of SiO2 particles became thicker, forming a thicker layer of SiO2 particles on PUM due to the accumulation of SiO2 particles, leading to a multilayer structure of SiO2 particles on the shell of SiO2@PUM. The formation mechanism of the raspberry-like SiO2@PUM was thoroughly discussed and ascribed to electrostatic attraction between the positively charged PU and negatively charged SiO2 particles. Once dried, SiO2@PUM was superhydrophobic and turned hydrophilic if water-wetted. Using a layer of SiO2@PUM, effective separation with good reusability for a variety of oil–water mixtures was achieved regardless of the oil density and types of oil–water emulsions. This work presents a novel protocol for the preparation of raspberry-like microspheres with tunable wettability via a rapid and green process, and the resulting microspheres are highly effective for the separation of diverse types of oil–water mixtures.