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Issue 18, 2017
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Super-hydrophobic covalent organic frameworks for chemical resistant coatings and hydrophobic paper and textile composites

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Abstract

Covalent organic frameworks are crystalline polymers with modular tunability and ordered pores. If made super-hydrophobic, owing to their flexibility, texture and organic nature, they can be of use in several applications that demand hydrophobic surfaces. Super-hydrophobic surfaces have been developed by introducing micro/nano-asperities on metal surfaces by laser-etching or by nano-structuring their morphologies. Many industrial applications demand super-hydrophobicity under chemically harsh environments, something which such metal-based metastable surfaces cannot guarantee. Evidently, the most abundant are metal-free fluorine based polymer surfaces, but considering long-term environmental benefits developing fluorine-free alternatives is important. Here, porous super-hydrophobic COFs with 2D and pseudo-3D frameworks have been utilized to make coatings with exceptional water-repelling characteristics assisted by their Cassie–Baxter state (contact angle = 163 ± 2°; tilt-angle = 2°, hysteresis = 4°). Importantly, the coatings maintain their super-hydrophobicity even under harsh acidic/basic conditions (pH = 1–14) and towards ice and hot water (80 °C), something where even a lotus leaf fails. Also, their organic nature and fibrous texture enable their facile compositing with paper and textiles. At a mere <5% loading, the COFs seem to pack very well within the cellulose strands of these materials providing a markedly hydrophobic coating to these otherwise completely hydrophilic materials.

Graphical abstract: Super-hydrophobic covalent organic frameworks for chemical resistant coatings and hydrophobic paper and textile composites

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Publication details

The article was received on 11 Feb 2017, accepted on 03 Apr 2017 and first published on 03 Apr 2017


Article type: Paper
DOI: 10.1039/C7TA01302G
Citation: J. Mater. Chem. A, 2017,5, 8376-8384
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    Super-hydrophobic covalent organic frameworks for chemical resistant coatings and hydrophobic paper and textile composites

    D. Mullangi, S. Shalini, S. Nandi, B. Choksi and R. Vaidhyanathan, J. Mater. Chem. A, 2017, 5, 8376
    DOI: 10.1039/C7TA01302G

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