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Silylation of Monolithic Resorcinol-Formaldehyde Xerogels

Henn, Fabian Alexander and Tannert, René and Milow, Barbara (2022) Silylation of Monolithic Resorcinol-Formaldehyde Xerogels. Seventh International Conference on Multifunctional, Hybrid and Nanomaterials, 2022-10-19 - 2022-10-22, Genua, Italien.

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Abstract

Hydrophobic materials are useful for many applications where liquids are involved. Phenolics represent a class of materials that is intrinsically hydrophilic due to the presence of free aromatic hydroxy groups. Due to their high porosity, phenolic aerogels and xerogels are particularly prone to absorb water and other polar liquids. This behavior includes the most prominent organic gels, based on resorcinol-formaldehyde (RF). However, few strategies to overcome the inherent hydrophobicity of RF gels are reported, and these are often limited to powders. Literature-known examples include the trimethylsilylation of powdered RF resulting in material that retain hydrophobic for a limited time. To this end, we report on the silylation of monolithic RF xerogels, using sterically demanding silyl reagents. Our synthetic studies include the variation of amine base and electronic nature of the silyl counterion. Characterization of the resulting gels by means of elemental analysis, X-ray photoelectron spectroscopy, pycnometry, sorption analysis, and scanning electron microscopy with electron-dispersive X-ray spectroscopy is presented. Furthermore, the wetting behavior of the silylated gels exemplified by their contact angle to water after exposure of the gels to ambient air and various liquids (water, acid and base) is discussed. Though apparently silylated to little extent, these gels retained significant hydrophobic behavior over the course of several months. Moreover, monoliths bearing sterically demanding silyl groups displayed higher stability towards aqueous acid than trimethylsilylated RF gels.

Item URL in elib:https://elib.dlr.de/189939/
Document Type:Conference or Workshop Item (Poster)
Title:Silylation of Monolithic Resorcinol-Formaldehyde Xerogels
Authors:
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
Milow, BarbaraUNSPECIFIEDhttps://orcid.org/0000-0002-6350-7728UNSPECIFIED
Date:21 October 2022
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:xerogels, hydrophobicity, silylation, resorcinol-formaldehyde
Event Title:Seventh International Conference on Multifunctional, Hybrid and Nanomaterials
Event Location:Genua, Italien
Event Type:international Conference
Event Start Date:19 October 2022
Event End Date:22 October 2022
Organizer:Elsevier
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 - NGC Fahrzeugstruktur II (old), 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:28 Nov 2022 08:50
Last Modified:24 Apr 2024 20:51

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