Ultra-fine Structure Control of Organic Crystals Using Solid-State Polymerization Reactions

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In this project, we have investigated the topochemical polymerization, dimerization, isomerization of unsaturated organic compounds as well as the phase transition and the intercalation reactions of the resulting polymer crystals, and revealed solid-state reaction mechanisms for controlling the reactions, structures, and properties of organic solid materials. We first investigated a change in the crystal structures and the accumulation of a strain in the crystals during the reaction to reveal the mechanism of the topochemical polymerization, EZ-photoisomerization, and [2+2] cyclodimerization of muconic esters as the 1,3-diene monomers via a crystal-to-crystal transformation. We proposed a solid-state reaction mechanism for the crystal-lattice controlled reactions of various unsaturated organic compound based on the results of in situ X-ray crystal structure analysis during the polymerization. Next, we prepared four kinds of stereoregular polymuconates by solid-state polymerization and revealed the reaction behavior and the layered structure of intercalation compounds. The orientation of the guest molecules is controlled according to the host polymer tacticity. We have fabricated the nanocomposite consisting of a crystalline organic polymer and fine metal particles. Furthermore, we developed a double-intercalation method using alkylamine and pyrene as the guests to control the fluorescence property in the solid state. An aromatic compound is separately introduced into the hydrophobic layers of the ammonium polymer crystals and shows a fluorescence emission from the single molecule, but not the excimer. We also found the thermochromism of polydiacetylenes in a solid film, polymer matrix, and solutions with a hysteresis loop as a function of temperature. They are accounted for by the formation of polymer aggregates and reorganization of the polymer chains.