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Synthesis of fluorine-modified polysilazanes via Si–H bond activation and their application as protective hydrophobic coatings

Furtat, P. and Lenz-Leite, M. and Ionescu, E. and Machado, R. A. F. and Motz, G. (2017):
Synthesis of fluorine-modified polysilazanes via Si–H bond activation and their application as protective hydrophobic coatings.
In: Journal of Materials Chemistry A, Royal Society of Chemistry, pp. 25509-25521, 5, (48), ISSN 2050-7488,
DOI: 10.1039/c7ta07687h,
[Online-Edition: https://doi.org/10.1039/c7ta07687h],
[Article]

Abstract

A new route to synthesize fluorine-modified polysilazanes for coating applications with improved hydrophobicity and excellent chemical resistance was developed by the reaction of commercially available liquid oligosilazane Durazane® 1800 and fluorinated alcohol 2,2,2-trifluoroethanol (TFE) using tetra-n-butylammoniumfluoride (TBAF) as a selective catalyst to activate Si–H groups for simultaneous selective reactions with both N–H and O–H groups. Calcium borohydride (Ca(BH4)2$2THF) was used as a reaction inhibitor, to terminate the reaction to obtain a solid, soluble fluorinated polysilazane, which is suitable for coating metal substrates via a simple dip-coating technique. The proposed reaction mechanisms and the resulting polymer structures confirm the attachment of the fluorinated groups on the polysilazane backbone; this was investigated by 1H and 13C NMR, FTIR, XPS, GPC, GC and elemental analysis. It was also demonstrated that the absence of catalysts leads only to the expected decomposition of the silazane by the alcohol. While the remaining silazane Si–H and Si–N bonds provide for an excellent adhesion of the coatings to the substrate, the CF3 groups decrease the surface energy leading to an increased contact angle of up to 15% and 40% to water and hexadecane, respectively, in comparison to fluorine-free polysilazane coatings. When tested as mold release coatings, the F-modified silazanes reduced the adhesion of a phenolic resin with an aluminum substrate from 12.7 to 2.8 MPa. Moreover, the chemical resistance of the fluorine-modified polysilazane based coatings in contact with acids and bases (HCl and KOH) is remarkably improved, offering great potential to protect metals from corrosion.

Item Type: Article
Erschienen: 2017
Creators: Furtat, P. and Lenz-Leite, M. and Ionescu, E. and Machado, R. A. F. and Motz, G.
Title: Synthesis of fluorine-modified polysilazanes via Si–H bond activation and their application as protective hydrophobic coatings
Language: English
Abstract:

A new route to synthesize fluorine-modified polysilazanes for coating applications with improved hydrophobicity and excellent chemical resistance was developed by the reaction of commercially available liquid oligosilazane Durazane® 1800 and fluorinated alcohol 2,2,2-trifluoroethanol (TFE) using tetra-n-butylammoniumfluoride (TBAF) as a selective catalyst to activate Si–H groups for simultaneous selective reactions with both N–H and O–H groups. Calcium borohydride (Ca(BH4)2$2THF) was used as a reaction inhibitor, to terminate the reaction to obtain a solid, soluble fluorinated polysilazane, which is suitable for coating metal substrates via a simple dip-coating technique. The proposed reaction mechanisms and the resulting polymer structures confirm the attachment of the fluorinated groups on the polysilazane backbone; this was investigated by 1H and 13C NMR, FTIR, XPS, GPC, GC and elemental analysis. It was also demonstrated that the absence of catalysts leads only to the expected decomposition of the silazane by the alcohol. While the remaining silazane Si–H and Si–N bonds provide for an excellent adhesion of the coatings to the substrate, the CF3 groups decrease the surface energy leading to an increased contact angle of up to 15% and 40% to water and hexadecane, respectively, in comparison to fluorine-free polysilazane coatings. When tested as mold release coatings, the F-modified silazanes reduced the adhesion of a phenolic resin with an aluminum substrate from 12.7 to 2.8 MPa. Moreover, the chemical resistance of the fluorine-modified polysilazane based coatings in contact with acids and bases (HCl and KOH) is remarkably improved, offering great potential to protect metals from corrosion.

Journal or Publication Title: Journal of Materials Chemistry A
Volume: 5
Number: 48
Publisher: Royal Society of Chemistry
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 15 Jan 2018 08:48
DOI: 10.1039/c7ta07687h
Official URL: https://doi.org/10.1039/c7ta07687h
Funders: We also thank CAPES (Coordenaç˜ao de Aperfeiçoamento de Pessoal de n´ıvel Superior) for financial support and Merck KGaA for the donation of the oligosilazane Durazane 1800.
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