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Hydrophobization of Monolithic Resorcinol-Formaldehyde Xerogels by Means of Silylation

Henn, Fabian Alexander and Tannert, René (2022) Hydrophobization of Monolithic Resorcinol-Formaldehyde Xerogels by Means of Silylation. Gels, 8 (5), pp. 304-315. Multidisciplinary Digital Publishing Institute (MDPI). doi: 10.3390/gels8050304. ISSN 2310-2861.

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Official URL: https://www.mdpi.com/2310-2861/8/5/304/htm


In materials research, the control of wettability is important for many applications. Since they are typically based on phenolics, organic aerogels, and xerogels are intrinsically hydrophilic in nature, and examples of the chemical functionalization of such gels are scarce and often limited to powders. This study reports on the silylation of monolithic resorcinol-formaldehyde (RF) xerogels using solutions of silyl chlorides and triflates, respectively, in combination with an amine base. The resulting gels are structurally characterized by means of elemental analysis, X-ray photoelectron spectroscopy, pycnometry, sorption analysis, and scanning electron microscopy with electron-dispersive X-ray spectroscopy. The wetting behavior of the silylated gels was studied by the determination of the contact angle to water after exposure of the gels to ambient air. Additionally, the uptake of liquid water and aqueous acids and bases was investigated. As a result, processes for the functionalization of RF xerogels with sterically demanding silyl moieties have been established. Although the analyses indicate that silylation occurred to a rather small extent, highly hydrophobic gels resulted which retained the wetting behavior over the course of several months with contact angles of >130°. Monoliths bearing sterically demanding silyl groups showed higher stability towards aqueous acid than trimethylsilylated RF gels.

Item URL in elib:https://elib.dlr.de/186426/
Document Type:Article
Title:Hydrophobization of Monolithic Resorcinol-Formaldehyde Xerogels by Means of Silylation
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Henn, Fabian AlexanderUNSPECIFIEDhttps://orcid.org/0000-0002-9768-399XUNSPECIFIED
Tannert, RenéUNSPECIFIEDhttps://orcid.org/0000-0001-9484-8886UNSPECIFIED
Date:16 May 2022
Journal or Publication Title:Gels
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
Page Range:pp. 304-315
EditorsEmailEditor's ORCID iDORCID Put Code
Fletcher, AshleighUNSPECIFIEDhttps://orcid.org/0000-0003-3915-8887UNSPECIFIED
Publisher:Multidisciplinary Digital Publishing Institute (MDPI)
Series Name:Advances in Xerogels
Keywords:xerogels; resorcinol-formaldehyde; functionalization; hydrophobicity
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Transport
HGF - Program Themes:Road Transport
DLR - Research area:Transport
DLR - Program:V ST Straßenverkehr
DLR - Research theme (Project):V - FFAE - Fahrzeugkonzepte, Fahrzeugstruktur, Antriebsstrang und Energiemanagement
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Aerogels and Aerogel Composites
Deposited By: Henn, Fabian Alexander
Deposited On:25 May 2022 09:06
Last Modified:25 May 2022 09:06

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