THE FACTORS CONTROLLING THE X-RAY INDUCED SOLID-STATE POLYMERIZATION-REACTIONS

本计画的目的是要厘清晶体中光子与电离辐射引发聚合反应的控制因素。本论文主要研究了结晶型2，5-二苯乙烯基吡嗪的2+2环加成反应。通过皮秒激光光解实验，我们发现准分子位置在反应中起着重要作用，它可能来源于晶格的不规则性。通过脉冲辐解观察到电子脉冲辐照产生类似的准分子，我们预期电离辐射也会发生类似的反应，实际上，这一点已被γ-<60>Co γ射线证实。因此，与光照射系统的情况相比，我们成功地通过在整个本体中照射晶体来更均匀地引发聚合反应。2.我们用ESR研究了聚乙烯两种不同模型化合物结晶n-C_8H_和c-C_ H_中电离辐射产生的自由基的异构化反应<18><13><28>，发现在三斜晶系和正交晶系晶体中，初始形成的初级自由基发生了热转化到倒数第二个烷基。从而阐明了控制交联反应发生在固体聚乙烯结晶部分的重要因素之一。

The purpose of this project is to clarify the factors controlling the polymerization reactions induced by photon and ionizing radiation in crystals.1. We mainly studied 2+2 cycloaddition reaction in crystalline 2,5-distyrylpyrazine which had been known as typical topochemical reaction. From the pico-second laser-photolysis measurements, we found that excimer sites, probably originated from irregularity of the crystal lattice, playd an important role in the reaction. From the observation by pulse radiolysis that the similar excimers were formed by the irradiation of electron pulse, we expected the similar reaction to be occurred by ionizing radiation ; actually, it was confirmed by using ^<60>Co gamma-ray. Thus, we succeeded in initiating the polymerization reaction more homogeneously, in comparison with the case of photo-illuminated systems, by irradiating crystal throughout the bulk. This last part of the results was summarized in the paper submitted to Bulletin of the Chemical Society of Japan on March 13,1997.2.We studied the isomerization reaction of radicals produced by ionizing radiation in two different model compounds of solid polyethylene, crystalline n-C_8H_<18> and c-C_<13>H_<28>, by using ESR.It was found that in the triclinic and the orthorhombic crystals the initially formed primary radicals were thermally converted to the penultimate alkyl radicals. Thus, one of the important factors which control the crosslinking reaction taking place in crystalline part of solid polyethylene was elucidated.