Fabrication of nanocrystals from diolefin derivatives and their solid-state photoreaction behavior

Nanocrystals of seven p-phenylenediacrylates, i.e., dimethyl (la), didecyl (lb), diundecyl (1c), ditetradecyl (1d), dipentadecyl (1e), dioctadecyl (1f), and dicholesteroyl (1g) derivatives, and 2,5-distyrylpyrazine (2) were fabricated by the reprecipitation method and their photochemical reaction behaviors were investigated in comparison to those of bulk crystals. The bulk crystals of 1a- 1c and 2 were found to be photoreactive, whereas those of 1d-1g were less photoreactive. In contrast, all of the nanocrystals of 1a-1g and 2 showed high photoreactivity. Nanocrystals of la and 2 were demonstrated to have the same packing as the corresponding polymerizable bulk crystals, and they gave the corresponding polymers by photoirradiation. The polymer crystal structures in their nanocrystals were confirmed to be the same as those in bulk crystals by X-ray and electron diffraction analyses. Their single-crystal-to-single-crystal transformation was established by their nanocrystallization. On the other hand, other nanocrystals (1b-1g) were found to have different packings compared with the corresponding bulk crystals. After photoirradiation, their crystallinity was degraded to form amorphous products.