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

本项目的目的是阐明控制光子和电离辐射在晶体中引发聚合反应的因素。我们主要研究了结晶2，5-二苯基吡嗪中的2+2环加成反应，这是一种典型的拓扑化学反应。从皮秒激光光解测量中，我们发现准分子位在反应中起着重要的作用，可能是由于晶格的不规则性引起的。从脉冲辐解观察到电子脉冲辐照形成了类似的准分子，我们预计电离辐射也会发生类似的反应；实际上，这一点得到了^&lt；60&gt；Co伽马射线的证实。因此，与光照射体系相比，我们成功地通过将晶体照射到整个块体来更均匀地引发聚合反应。用ESR研究了电离辐射产生的自由基在两种不同的固体聚乙烯模型化合物中的异构化反应，它们分别是晶态n-C_8H_&lt；18&gt；和c-C_&lt；13&gt；H_&lt；28&gt；。从而阐明了控制固体聚乙烯结晶部分发生交联反应的重要因素之一。

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.