Plastic crystal
[1][2] POIPCs are solid protic organic salts formed by proton transfer from a Brønsted acid to a Brønsted base and in essence are protic ionic liquids in the molten state, have found to be promising solid-state proton conductors for high temperature proton-exchange membrane fuel cells.[3] X-ray diffraction patterns of plastic crystals are characterized by strong diffuse intensity in addition to the sharp Bragg peaks.[1] In a powder pattern this intensity appears to resemble an amorphous background as one would expect for a liquid,[1] but for a single crystal the diffuse contribution reveals itself to be highly structured.Recent advances in two-dimensional detection at synchrotron beam lines facilitate the study of such patterns via techniques such as small-angle X-ray scattering.[5] Some plastic crystals, like aminoborane, when subjected to mechanical stress, exhibit behavior similar to ductile metals such as lead, gold, silver, or copper.