Abstract
The polycondensation sol–gel reaction of 5-methylresocinol and formaldehyde with additional compounds in reaction media is a relatively simple way to produce modified aerogels. In order to obtain aerogels with a large surface area and high porosity, the conditions for gel formation, the solvent exchange process before drying, and the supercritical drying process were optimized. A successful attempt was made to introduce ferrocene units into 5-methylresocinol-formaldehyde-based aerogels. The resulting aerogels are amorphous substrates, and no aggregated ferrocene units were found in their structures. All of the aerogel samples that were obtained are structurally similar despite differences in the original ferrocene units and their initial concentration. It was found that the inclusion limit of ferrocene structural blocks into an aerogel is ~6% wt. The structures of the inclusions in which all of the Fe atoms in the aerogel substrates were present in ferrocene/ferrocenium at an approximate ratio of 60/40 to 55/45 were confirmed by X-ray photoelectron spectroscopy and Mössbauer spectroscopy. Aerogels with ferrocene/ferrocenium inclusions are likely to exhibit reversible redox activity in reactions with gaseous reagents.
Highlights
Aerogels—the nanoscale skeletal structure of which forms a solid macroscopic state—are known to exhibit unique properties
A comparison of the IR spectra of different aerogels reveals a close similarity of Fc-aerogels to the resorcinol–formaldehyde aerogels studied previously (Figure S1 in Supplementary Materials)
The results show a general course of degradation characteristic of resorcinol–formaldehyde aerogels [29]—a similar smooth process of degradation for every sample (Figure S4))
Summary
Aerogels—the nanoscale skeletal structure of which forms a solid macroscopic state—are known to exhibit unique properties. It has been proposed that highly nanoporous aerogels be recognized “as a state of matter rather than as a functional material, because of its qualitative differences in bulk properties, transitional density and enthalpy between liquid and gas and diverse chemical compositions” [1]. Resorcinol–formaldehyde (RF) aerogels are well-known organic aerogels with various applications, mainly as precursors to electrically conductive carbon aerogels [2,3,4]. RF aerogels are typically prepared using Pekala’s method, followed by drying with supercritical CO2 [5]. Supercritical drying preserves the original porosity of the hydrogel to a substantial degree and can be used on an industrial scale [8]. Supercritical drying is often the preferred method that
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