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

本课题的目的是阐明晶体中光子和电离辐射引起的聚合反应的控制因素。主要研究了结晶2,5-二酰基吡嗪的2+2环加成反应，该反应被认为是典型的拓扑化学反应。从皮秒激光光解测量中，我们发现准分子位点在反应中起重要作用，可能是由于晶格的不规则性。从脉冲辐射分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，它是用^<60>Co伽马射线证实的。因此，与光照射系统相比，我们通过在整个体中照射晶体，成功地使聚合反应更加均匀地开始。最后一部分的结果在1997年3月13日提交给日本化学学会公报的论文中进行了总结。用ESR研究了电离辐射在固体聚乙烯n-C_8H_<18>和c- c__< 13>H_<28>两种不同模型化合物中自由基的异构化反应。发现在三斜晶和正交晶中，最初形成的初级自由基被热转化为倒数第二烷基自由基。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.