Linear acetylenic carbon

This polymeric carbyne is of considerable interest to nanotechnology as its Young's modulus is 32.7 TPa – forty times that of diamond;[4] this extraordinary number is, however, based on a novel definition of cross-sectional area that does not correspond to the space occupied by the structure.

Carbyne has also been identified in interstellar space; however, its existence in condensed phases has been contested recently, as such chains would crosslink exothermically (and perhaps explosively) if they approached each other.

[9] During the past thirty five years an increasing body of experimental and theoretical work has been published in the scientific literature dealing with the preparation of carbyne and the study of its structure, properties and potential applications.

[12] This material was found to consist entirely of carbon and its hexagonal cell dimensions matched those reported earlier for carbyne by Russian scientists.

They were claimed to be reasonably stable, even against moisture and oxygen, as long as the terminal alkynes on the chain are capped with inert groups (such as tert-butyl or trifluoromethyl) rather than hydrogen atoms.

[5] Another 1995 report claimed detection of carbyne chains of indeterminate length in a layer of carbonized material, about 180 nm thick, resulting from the reaction of solid polytetrafluoroethylene (PTFE, Teflon) immersed in alkali metal amalgam at ambient temperature (with no hydrogen-bearing species present).

[19] Also, thermal decomposition of copper acetylide in vacuum yielded a fluffy deposit of fine carbon powder on the walls of the flask, which, on the basis of spectral data, was claimed to be carbyne rather than graphite.

The chains were grown inside double-walled carbon nanotubes, and are highly stable protected by their hosts.

[24] As of 2010, the longest such chain in a stable molecule had 22 acetylenic units (44 atoms), stabilized by rather bulky end groups.

[26] The highly symmetric carbyne chain is expected to have only one Raman-active mode with Σg symmetry, due to stretching of bonds in each single-double pair[clarification needed], with frequency typically between 1800 and 2300 cm−1,[18] and affected by their environments.

[32] The comparison with experimental data obtained for short chains in gas phase or in solution demonstrates the effect of the DWCNT encapsulation, leading to an essential downshift of the band gap.