BARRIERS TO FLOW IN SEMICRYSTALLINE IONOMERS - A PROCEDURE FOR PREPARING MELT-PROCESSED PERFLUOROSULFONATE IONOMER FILMS AND MEMBRANES

A procedure for preparing a melt-processable form of perfluorosulfonate ionomers is presented. The melt-flow Properties of the melt-processable polymer are attributed to the elimination of polymer crystallinity and strong electrostatic crosslinks which act as barriers to flow in semicrystalline ionomers. The ''PTFE-like'' crystallinity is removed by evaporation of the ionomer solutions, and the electrostatic crosslinks are weakened by neutralizing the ionomer with large, hydrophobic tetrabutylammonium counterions. To yield the desirable melt-flow properties, the bulky counterions function as internal plasticizers and form weak ion pair dipoles which diminish the attractive forces responsible for ionic aggregation. Fabrication procedures and the results of preliminary characterization studies of melt-processed films and membranes are discussed here.