1000 at 1000: the lightest bakelite and beyond
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1000 at 1000: the lightest bakelite and beyond Ca˘ta˘lin Croitoru1,* 1
Department of Materials Engineering and Welding, Transilvania University of Brasov, Eroilor 29 Blvd., 500036 Brasov, Romania
Ó
Springer Science+Business
Media, LLC, part of Springer Nature 2020
Organic aerogels represent a unique category of carbon materials. They are the lightest solids in existence, not much denser than the air on a foggy morning. They may sound like next to nothing, but they certainly are stronger than they look. A piece of this material can withstand over 4000 times its own weight. Unlike any other porous materials, their composition, chemical properties and porosity can be built from scratch (like polymers can be made from smaller building blocks) to match practically any specific application through carefully controlling the synthesis conditions [1–3]. Highly efficient supercapacitors and catalysts are now obtained starting from these organic aerogels, and it was all possible thanks to a very humble material, not much different in chemical composition than the commonplace phenolic resin. These aerogels did not stay in their box for long. As quick as a flash photograph or starting a car takes (on a materials development timeframe), they managed
to ‘‘glue themselves’’ (since phenolic resins are also adhesives) to their inorganic counterparts, creating new (sticky) bridges between the organic and the inorganic realms. Through combining the excellent toughness, flexibility and high surface area of organic aerogels with the thermal stability of inorganic aerogels, unique materials can be tailored. The first aerogels (both inorganic and organic) were prepared since the early 1900s by T. Graham and S. Kistler (the latter coining the term ‘‘aerogel’’). Organic aerogel-like materials were obtained through solvent exchange and supercritical drying of various polymeric gels (pectin, albumin, cellulose, agar, nitrocellulose, polystyrene and so forth) [2]. To be fair, however, since the starting polymer gels underwent significant collapsing and pore shrinkage in the solvent exchange step, they should be included in the category of xerogels by the current terminology.
This editorial is part of our series ‘‘1000 at 1000’’, highlighting the Journal of Materials Science’s most highly cited publications as part of the journal’s celebration of 1000 issues. In this issue: ‘‘Organic aerogels from the polycondensation of resorcinol with formaldehyde’’ by Richard W. Pekala (then) of Lawrence Livermore National Laboratory from California, the U.S. [1].
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05038-y
J Mater Sci
These wonderful materials never actually found their place in the world until the late 1980s. For nearly four decades since their first successful synthesis attempt, Kistler’s statement that ‘‘apart from the scientific significance, the new physical properties developed in the materials are of unusual interest’’ held [2]. Even if various applications were envisaged over the year
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