Low Equivalent Weight Ionomer

Abstract

An ionomer and a process for forming the ionomer such that the ionomer has (1) low equivalent weight (below 950, preferably between 625 and 850, and most preferably between 675 and 800) and (2) high conductivity (greater than 0.13 S/cm). In another embodiment, the invention is an ionomer having (1) low equivalent weight (below 950, preferably between 625 and 850, and most preferably between 675 and 800) and (2) acceptably low hydration (less than about 120 weight percent). These ionomers are capable of being processed into thin film and are extremely well-suited for low humidity or high temperature fuel cell applications.

We claim: 
     
         1 . A product produced by a process comprising the steps of:
 a) forming a mini-emulsion of a mixture of deionized water, a perfluorinated surfactant, optionally dissolved in an aqueous solution, a liquid perfluorinated hydrocarbon having a molecular weight below 2000 and an ionomeric monomer;   b) pressurizing said emulsion in an agitated reactor with at least one substantially fluorinated alkene gas;   c) initiating polymerization with a free radical initiator in said reactor; and   d) maintaining a known pressure of the substantially fluorinated alkene gas for a period of time.   
     
     
         2 . The product of  claim 1  wherein said product has an equivalent weight between about 600 and about 950, and wherein the ionic conductivity of the acid form of a membrane hydrated at room temperature prepared from said product is greater than about 0.13 S/cm at room temperature.