2. Chemistry of High-Energy Charged Particles: Radiations and Polymers

As reviewed in Chap. 1, the energy released by a charged particle in the limited spatial area is extremely huge in comparison with the energy of chemical bondings. However, the area is nm-sized and nothing happens out of the area, leading to the relatively small amount of the energy given by the charged particle in comparison with the thermodynamic energy averaged over the total volume and mass of the target materials. This suggests it hard to induce stoichiometric reaction in the molecular materials by the radiation chemical processes. Radiations met polymeric materials at an early era of the radiation physical chemistry in the beginning of twentieth century, where the drastic physical property change of the polymer materials was caused by the relatively small number (non-stoichiometric) of the reaction points to the total amount of substance in the target formed by radiation chemical processes. The combination of macromolecules and radiations were so-called the “best-match,” and developed into radiation processing of rubbers and the other polymeric materials. The basic aspects of the radiation chemical processes in macromolecular materials are overlooked in this chapter, and the unique feature of chemical reactions traced by bulk analysis is discussed in case of high-energy charged particle, inspiring “materials fabrication by A particle” discussed in the following chapter.