Heavy ion tracks in fluoropolymer film; Recent developments and future prospects

Yamaki, Tetsuya; Nuryanthi, N.*; Koshikawa, Hiroshi; Asano, Masaharu*; Sawada, Shinichi; Kitamura, Akane; Maekawa, Yasunari; Kay-Obbe, V.*; Severin, D.*; Seidl, T.*; Trautmann, C.*

Practically, polyvinylidene fluoride (PVDF) has been said to be the only fluoropolymer in which ion tracks can be developed by chemical etching. We thus investigated the possibility of varying the beam parameters and applying the effect of a pre-etching treatment for PVDF ion-track membranes with the goal of achieving enhanced track etching for effective control of the pore size and shape. Our activities also cover all types of fluoropolymers including PVDF. Compared to PVDF, poly(ethylene--tetrafluoroethylene) and a series of perfluoropolymers are known to be very stable in highly-concentrated acid or alkaline solutions or at higher temperatures. Although this property might make their ion-track etching very challenging, the ongoing research is expected to allow one to accumulate know-how on methods of chemical etching, which can be generalized for the chemical structures. These will give feedback to a guiding principle for effective ion-track etching in fluoropolymers.