Pressure-induced acetylene polymerization

Fig. 17. Pressure-induced polymerization of acetylene. Snapshots of one plane (a) 9 GPa and 400 K, (b) intermediate configuration at 25 GPa and 400 K, and (c) final configuration at 25 GPa and 400 K. Reprinted with permission from Bernasconi et al. (1997).

Tabata, M. Tanaka, Y Sadahiro, Y Sone, T. Yokota, K. Miura, 1. Pressure-induced cis to trans isomerization of aromatic polyacetylenes. 2. Poly((e-ethoxyphenyl)acetylene) stereoregularly polymerized using a Rh complex catalyst. Macromolecules 1997, 30, 5200-5204. 

Simply increasing the acetylene pressure to beyond a GPa at room temperature inside a diamond anvil will induce self-polymerization [53-55]. Analysis of the resulting materials by Raman spectroscopy indicates that trans-PA is formed predominantly under these conditions, presumably due to steric reasons trans-PA packs better than cis-PA). 

Acetylene has been observed in the atmospheres of Jupiter and Titan [33, 34] and more recently has been identified in significant abundance in comet Hyakutake [35]. Following the discovery of acetylene in Hyakutake, photochemical experiments have demonstrated [36] that this molecule is a likely precursor of C2, a widely observed component of comets. Acetylene itself may therefore be a ubiquitous constituent of comets. It has been proposed [37] that polymerization of acetylene in cometary impact on planetary atmospheres may be responsible for the formation of polycyclic aromatic hydrocarbons (PAHs) which may in turn be responsible for the colors of the atmospheres of Jupiter and Titan. Shock-induced polymerization of acetylene has been observed in the gas phase [38], and static high-pressure experiments have demonstrated polymerization of orthorhombic solid acetylene above 3 to... 

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