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Pressure, as well as temperature, is a major parameter determining the state of substances. It can be used, for example, to convert gases into liquids or solids. From a microscopic viewpoint, pressure can provide a reaction field controlling the motion and arrangement of molecules. When pressure is further applied to a crystal consisting of orderly arranged molecules, an interesting change occurs in chemical bonding. In the case of hydrogen cyanide (HCN) having C-N triple bond, polymerization reaction occurs under thousands of atmospheric pressures and at room temperature. The colorless crystal of HCN changes into a reddish brown polymer as seen in the photo. High-pressure solid-state polymerization is a new process requiring neither polymerization initiators nor catalysts, and is expected to produce new functional polymers such as conducting ones.
Microscopeic photos of hydrogen cyanide in a high-pressure cell Top photo shows molecu ar crystal under 2,000 atmospheric pressures at room temperature: bottom photo shows polymerization reaction process under 7,000 atmospheric pressures at room temperature. |