Phenolic Aerogels And Their Carbonization
Phenolic aerogels comprise an important class of organic aerogels with potential for use in thermal superinsulation applications and which serve as precursors to electrically conducting carbon aerogels of importance to applications including filtration, energy generation (e.g., electrodes in fuel cells), energy storage (e.g., electrodes for batteries and supercapacitors), and other green energy technologies. Historically, the most important variety of phenolic-resin-based aerogels has been based on resorcinol-formaldehyde (RF) chemistry, but in recent years aerogels based on polybenzoxazine (PBO) chemistry have become increasingly important as well. In this chapter, we present a broad overview of these materials, focusing on how the chemical, microscopic, and macroscopic characteristics of RF aerogels, and thereby carbon aerogels, can be tailored to achieve desired application-specific structure-property relationships via variation of processing conditions such as monomer chemical identity, monomer concentration, pH, and catalyst-to-monomer ratio. Emphasis is placed on chemical transformations that occur during processing as well as on how chemical composition and structure drive materials properties. Discussion of PBOs focuses on a recently developed room-temperature acid-catalyzed synthetic route that enables deconvolution of polymerization of the monomer from subsequent curing steps, which led to the discovery of ring-fusion aromatization as a reaction pathway available to benzoxazine monomers that proves to be a main property-determining factor during subsequent carbonization. Ring-fusion aromatization in PBOs was extended to and its effect studied in other mainstream phenolic aerogels derived not only from resorcinol but also from phenol and from phloroglucinol.
C. Sotiriou-Leventis et al., "Phenolic Aerogels And Their Carbonization," Springer Handbooks, pp. 479 - 506, Springer, Jan 2023.
The definitive version is available at https://doi.org/10.1007/978-3-030-27322-4_20
Keywords and Phrases
Acid catalysis; Aromatization; Base catalysis; Carbon aerogels; Carbonization; Formaldehyde; Phenol; Phenolic aerogels; Phloroglucinol; Polybenzoxazine; Resorcinol; Terephthalaldehyde
International Standard Serial Number (ISSN)
Article - Journal
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01 Jan 2023