Clarification of Proton Conduction Processes in Radical-doped Perfluorosulfonic Acid Ion Exchange Membranes Using Elastic Recoil Detection Technique

通过直流电阻和交流阻抗测量，发现了全氟磺酸膜在室温空气中以高达约50 kGy的剂量进行γ射线辐照的新的质子传导过程。在300 K在空气中的膜的电导率提高到约三个数量级高于未照射的膜的电导率。通过弹性反冲探测（ERD）技术，观察到在辐照聚合物的近表面区域中的氢含量增加到未辐照聚合物的两倍。此外，通过水接触角测量发现，由于亲水自由基的产生，吸水特性增强。通过紫外、可见和红外光吸收以及氢离子交换容量测量，发现辐射诱导的缺陷，如氟碳和过氧自由基，羰基中的C=O键与新的质子传导过程有关。由于近表面区域的辐射诱导缺陷的氢吸收特性的修改导致质子导电性的增强。

New protonic conduction processes of perfluorosulfonic acid membranes by gamma-ray irradiation at a dose of up to approximately 50 kGy at room temperature in air have been found by direct current resistance and alternative current impedance measurements. The conductivities of the membranes at 300 K in air were enhanced to approximately three orders of magnitude higher than the conductivities of an unirradiated membrane. The hydrogen content in the near-surface region of the irradiated polymers was observed to increase to twice that of the unirradiated polymer by using the elastic recoil detection (ERD) technique. In addition, it was found by the water contact angle measurements that the water absorption characteristics were enhanced due to the production of hydrophilic radicals.By means of ultraviolet, visible, and infrared optical absorption and by hydrogen-ion-exchange capacity measurements, it was revealed that radiation-induced defects such as fluorocarbon and peroxy radicals, and C=O bonds included in carbonyl groups were related to the new proton conduction processes. The modification of hydrogen absorption characteristics due to the radiation-induced defects in near-surface regions leads to the enhancement of the proton conductivity.