Exploring the structure of a hydrogen cyanide polymer by electron spin resonance and scanning force microscopy

Abstract

Summary: Aqueous solutions of potassium cyanide and ammonium hydroxide are known to yield a heterogeneous cyanide polymer, containing paramagnetic sites and biologically significant substructures including polypeptides. Here, such solutions were used to prepare various samples of polymer for study by X-band and W-band electron spin resonance (ESR), scanning electron microscopy (SEM), and scanning force microscopy (SFM). Elemental composition of a typical sample of the polymer was C-35.2%, N-38.47%, O-14.51%, and H-4.13%, exposing the polymer to 6M HCl hydrolyzed portions of the polymer and released glycine and traces of other amino acids. The X-band ESR spectra consist of a single slightly asymmetric line centered at g = 2.003; spin concentration measurements made at X-band using a nitroxide radical standard yield approximate radical concentrations of 10 18 spins/gm. W-band ESR indicates the presence of a single rhombic paramagnetic site with g x = 2.0025, g y = 2.0030, and g z = 2.0048 and the possibility of small 14 N hyperfine splittings. The ESR spin echo studies yield a longitudinal relaxation time, T 1, of 75 µS and a short-phase memory relaxation time, T m , of about 300 nS. Scanning electron microscopy studies of the polymer show that it is made of ellipsoidal particles about one micron in size. The particles tend to clump together when suspended in aqueous solution. The particles disperse and dissolve in dimethyl sulfoxide (DMSO); when these solutions dry on microscope slides, optical microscopy shows a branched island morphology for the polymer. This morphology is reminiscent of snowflakes and is identified as dendritic. Phase contrast SFM of the dendritic arms show a striking segregation and ordering of various components of the polymer. Paramagnetic sites are conserved in the series of steps leading to dendritic structures.

Thermal characterization of HCN polymers by TG–MS, TG, DTA and DSC methods

“…Our results are comparable to those reported by Eastman et al [27] for short reaction times (1e10 days). For longer reaction times (30 days) a black, insoluble solid richer in oxygen was obtained.…”

A Comparative Study on HCN Polymers Synthesized by Polymerization of NH4CN or Diaminomaleonitrile in Aqueous Media: New Perspectives for Prebiotic Chemistry and Materials Science

“…This kinetic behaviour in both series led us to perform new experiments to explore how the polymerization time affects the conversion for both monomers. The concentrations of 1 m for the NH 4 CN series and 0.25 m for the DAMN series were chosen because they lead to higher conversion for a constant reaction time of 96 h. As observed in Figure b, the conversions of approximately 35–39 % for the production of NH 4 CN polymers were comparable to those reported previously . Longer reaction times did not lead to an increase in conversion as expected, because the limit of conversion at 80 °C is achieved after 24 h .…”

New Insights into the Characterization of ‘Insoluble Black HCN Polymers’

“…-The results of the elemental analyses of the insoluble black HCN polymers are compiled in Table 1. Our results are comparable to those reported by Eastman et al [23] and Labadie et al [24] for short reaction times (1 -10 d). For longer reaction times (30 d), black insoluble solids richer in oxygen were obtained.…”