Anisotropic surface eruptions on polymerized diacetylene crystals†

Surface eruptions that are approximately 0.5 μm in diameter at the base and about 700 Å in height have been observed by atomic force microscopy on single crystals and films of polydiacetylenes of the alkylurethanes of 5,7-dodecadiyn-1,12-diol when the polymerization is performed using ⁶⁰Co gamma radiation in the presence of air. The eruption process is associated with monomer polymerization and is anisotropic, as the eruptions are found only on the (100) face of single crystal specimens. Crystals having surface eruptions are irreversibly converted from blue to red at room temperature on exposure to a single pulse of 532 nm laser light while crystals lacking eruptions do not undergo this change.