Preparation of fluoropolymer-based ion-track membranes; Structure of latent tracks and pretreatment effect

Yamaki, Tetsuya; Nuryanthi, N.*; Koshikawa, Hiroshi; Sawada, Shinichi; Hakoda, Teruyuki; Asano, Masaharu; Maekawa, Yasunari; Voss, K.-O.*; Severin, D.*; Seidl, T.*; Trautmann, C.*

We examined chemical structures of the defects in an ion track penetrating through poly(vinylidene fluoride) (PVDF), and accordingly, presented a pretreatment technique for achieving more efficient track etching. A 25 m-thick PVDF film was bombarded with 1.1 GeV U or 450 MeV Xe ions. According to the infra-red spectroscopy and residual gas analysis, the formation of many double bonds were found to occur in the PVDF main chain with the evolution of hydrogen fluoride. The knowledge of the solubility in a permanganate alkaline solution and our preliminary experiment suggested the importance of oxidized tracks for the easy introduction of the etching agent. We finally found that the pretreatment with ozone could oxidize the double bonds in the tracks, thereby vigorously promoting track etching before breakthrough.