HCN-Derived Polymers: From Prebiotic Chemistry to Materials Science

Hydrogen cyanide (HCN)Hydrogen cyanide (HCN)-derived polymers are a diverse family of complex substances. In laboratory settings, these polymers can be synthesized usingLiquid HCN liquid HCNHydrogen cyanide (HCN), which readily undergoes polymerization in the presence of bases such as NH3 or Et3N, as well as free radicals generated by ionizing radiation. Moreover, their formation is observed across a broad spectrum of temperatures, pressures, solvents, and mineral surfaces. This unique polymer system can also be derived from its soluble salts (NaCN or KCN), its trimer and tetramer counterparts—aminomalononitrile (AMN) and diaminomaleonitrileDiainomaleonitrile (DAMN), respectively—or from hydrolysis byproducts like formamide. Furthermore, it has been suggested that HCN polymers may be the major components of the dark matter present on the surface of meteorites and comets. Interestingly, they have significant implications for the prebiotic generation of several important bioorganics, such as amino acids, canonical and non-canonical nucleobases of interest in the “pre-RNA and RNA world” hypotheses (where RNA is the ribonucleic acid), carboxylic acids present in the reverse citric acid cycleCitric acid cycle, and cofactors such as pteridines. Hence, there is a proposition suggesting that HCN polymers might have played a significant role in the initial phases of chemical evolution leading to life. Conversely, the precise structures of these polymers have not been completely elucidated and remain subject to controversy, largely owing to their sensitivity to the particular synthetic conditions employed for their production. Indeed, recent investigations into kinetics and characterization have unequivocally demonstrated a direct correlation between synthetic parameters and the spectroscopic, thermal and textural characteristics of polymers derived from HCN. Consequently, the correct selection of polymerization settings can lead to the proper tuning of the properties of the macrostructures and, by extension, it could be possible to develop new smart and multifunctional materials. In this way, currently, there is a growing interest in the potential applications of these macromolecules in materials science due to their biocompatibility as coatings and adhesives of interest in biomedicine. They have also been proposed as valuable compounds in designing semiconductors, ferroelectric materialsFerroelectric material and catalyzersCatalysers, and as protective coatings against corrosion. In addition, these polymers present some similar characteristics to well-known carbon nitrides, which have a large profile of applications in materials science. In this chapter, a general overview from the first HCN oligomerization observed by Proust in 1806 to the most recent advances in materials science and new proposed insights in prebiotic chemistry will be reported.