A Comprehensive Review of HCN-Derived Polymers

Abstract

HCN-derived polymers are a heterogeneous group of complex substances synthesized from pure HCN; from its salts; from its oligomers, specifically its trimer and tetramer, amino-nalono-nitrile (AMN) and diamino-maleo-nitrile (DAMN), respectively; or from its hydrolysis products, such as formamide, under a wide range of experimental conditions. The characteristics and properties of HCN-derived polymers depend directly on the synthetic conditions used for their production and, by extension, their potential applications. These puzzling systems have been known mainly in the fields of prebiotic chemistry and in studies on the origins of life and astrobiology since the first prebiotic production of adenine by Oró in the early years of the 1960s. However, the first reference regarding their possible role in prebiotic chemistry was mentioned in the 19th century by Pflüger. Currently, HCN-derived polymers are considered keys in the formation of the first and primeval protometabolic and informational systems, and they may be among the most readily formed organic macromolecules in the solar system. In addition, HCN-derived polymers have attracted a growing interest in materials science due to their potential biomedical applications as coatings and adhesives; they have also been proposed as valuable models for multifunctional materials with emergent properties such as semi-conductivity, ferroelectricity, catalysis and photocatalysis, and heterogeneous organo-synthesis. However, the real structures and the formation pathways of these fascinating substances have not yet been fully elucidated; several models based on either computational approaches or spectroscopic and analytical techniques have endeavored to shed light on their complete nature. In this review, a comprehensive perspective of HCN-derived polymers is presented, taking into account all the aspects indicated above.

Tuning the Morphology in the Nanoscale of NH4CN Polymers Synthesized by Microwave Radiation: A Comparative Study

“…The conversion values for polymers 6 , 7 and 9 was really unexpected, reaching yields similar to those obtained by means of a traditional heating process [ 1 , 14 ]. This behavior of the polymerization in the presence of MW radiation seems to indicate significant differences with respect to the kinetic approach reported using conventional heating, in which a clear limit conversion was observed after a concrete reaction time for a fixed temperature [ 4 ]. Further works are in progress to study in detail the kinetic behavior of the MW-driven polymerization of cyanide.…”

“…In addition, the pathways proposed to explain the formation of NH 4 CN polymers in aqueous media suggest collateral reactions during the course of this precipitation polymerization, such as deaminations, denitrogenations, dehydrocyanations, hydrolysis and oxidations. These last processes are responsible for the incorporation of oxygen in the macrostructures [ 4 ], which would lead to a gain of weight considering the total initial mass input in the system (the initial weight of NaCN plus NH 4 Cl). Figure 2 b shows the weight balance found in both series, considering the reaction conditions shown in Table 1 , based on the following formula: Weight Balance (%) = [(weight NaCN + weight NH 4 Cl) − (gel fraction weight + freeze-dry sol content)]/(weight NaCN + weight NH 4 Cl)]·100.…”

“…Recently, it has been shown that the particle morphology of the known HCN-derived polymers can be tuned by the choice of the synthetic conditions [ 1 , 2 , 3 ]. Some polymers of this heterogeneous family [ 4 ] have been proposed as emergent materials with different applications, such as photocatalysts [ 5 ], semiconductors, nanowires, ferroelectric materials [ 6 ], capacitors [ 1 ], coatings with potential biomedical applications [ 2 , 7 , 8 , 9 ], protective films against corrosion [ 10 , 11 ], or for the development of antimicrobial media for passive filtration [ 12 ].…”

The Beginning of HCN Polymerization: Iminoacetonitrile Formation and Its Implications in Astrochemical Environments

“… 1 , 23 − 25 HCN-derived polymers are also of interest as functional materials, e.g., in catalysis or as adhesives and coatings for biomedical applications. 13 , 22 Given the presumed key role of iminoacetonitrile in prebiotic chemistry, it is important to answer the questions: where can this molecule form and how?…”

NMR Properties of the Cyanide Anion, a Quasisymmetric Two-Faced Hydrogen Bonding Acceptor

“…As a result, its orientation in crystalline cyanide salts is often disordered [7][8][9][10][11]. The same feature is responsible for the polymerization of hydrogen cyanide, resulting in materials with different characteristics and properties [12][13][14][15]. Dimers [16][17][18] and linear clusters [19,20] of hydrogen cyanide, its crystal structure [21], and its aggregates with the cyanide anion [22] and other proton acceptors [23][24][25][26] were studied both experimentally and theoretically.…”