Degradation manner of polymer grafts chemically attached on thermally stable polymer films; Swelling-induced detachment of hydrophilic grafts from hydrophobic polymer substrates in aqueous media

Enomoto, Kazuyuki*; Takahashi, Shuichi*; Iwase, Takanori*; Yamashita, Takashi*; Maekawa, Yasunari

The degradation manner of graft-type polymer electrolyte membranes consisting of hydrophilic poly(styrenesulfonic acid) (PSSA) graft polymers (grafts) and thermally and mechanically stable hydrophobic polymer substrates was examined in hot water. Severe weight loss was observed in PSSA-grafted cPTFE and ETFE films but not in a PSSA-grafted PEEK film. The decomposed extracts in water were characterized as PSSA during the whole course of degradation, clearly showing that the PSSA grafts detached from the fluorinated substrates without decomposition or scission of graft polymer chains. This is quite a new degradation manner for graft-type polymer electrolyte membranes; namely, hydrophilic PSSA grafts detach from hydrophobic polymer substrates due to swelling-induced stress at the interfacial boundary in the grafted films.