CRYSTAL STRUCTURE OF AROMATIC DIACETYLENE DERIVATIVES AND REACTIVITY OF SOLID-STATE POLYMERIZATION Y.Shibamoto^*, K.Yano, N.Kanehisa, Y.Yamamoto⁺, S.Tagawa⁺, Y.Kai, Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565, Japan, ⁺The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567, Japan

Some diacetylene compounds are known to undergo solid-state polymerization upon heating, irradiation or mechanical stimulation, and give single crystals of conjugated polymer. The reactivity of a diacetylene in the crystalline state is governed by the molecular packing of the monomer. Only those diacetylenes which have suitable packing conditions will undergo facile polymerization. The single crystals of these conjugated polymer have attracted attention on their physical properties, such as conductivity, optical nonlinearity, and mechanical strength.

We have investigated the correlation between the crystal structure and the reactivity in solid-state polymerization of various aromatic acetylene derivatives. We reported the crystal structures of some diethynylbenzene derivatives and interpreted the characteristic features of them in the solid-state polymerization upon irradiation with gamma-ray based on the unique monomer packings (Y.Kai, A.Yamamoto, D.Xu, N.Kasai, M.Hagihara, Y.Yamamoto, S.Takahashi and K.Hayashi, Makromol. Chem. 1987. 188, 3047-3059). Recently, we have synthesized the aromatic diacetylene derivatives, 1-(5-hydroxypenta-1,3-diynyl)-4-ethynylbenzene(I), 1,4-bis-(5-hydroxypenta-1,3-diynyl)-benzene(II), and 1,2-bis-(5-hydroxypenta-1,3-diynyl)-benzene(III), and obtained these single crystals. So the crystal structures of I, II and III were determined by X-ray diffraction method. As a result, it was found that the monomer molecules in the crystals of both I and II take suitable packing structures to undergo solid-state polymerization, but in the crystal of III, the monomer molecules are arranged not so as to undergo solid-state polymerization. With respect to the crystal of I, monomer arrangement is suitable for solid-state polymerization not only between diacetylene moieties but also ethynyl ones. The distance between the neighboring ethynyl moieties is nearer than that between diacetylene ones. So stepwise polymerization may be reasonable, first between ethynyl moieties, next between diacetylene ones.