Proton exchange membranes (PEMs) containing phosphonic acid groups are very promising because of the potential advantage of achieving a high proton conductivity while maintaining its composition through a Grotthus-like network of donor/acceptor groups at temperatures greater than 100 ^oC.

As a first step towards the synthesis of optimal fluorinated PEM ionomers, we synthesized fluorine containing model compounds of phosphonic acids of the type, F(CF₂)_nPO(OH)₂ (n = 1,3,4) , (OH)₂OPCF₂PO(OH)₂ and (C₄F₉)₂PO(OH). ¹⁹F, ¹H, and ³¹P NMR, and TGA were used for characterization of these materials. They are very strong acids, and exhibit a high degree of stability at elevated temperatures. The proton conductivity studies for these model compounds were done under a wide range of conditions of temperature and water content (humidity). In this presentation we will discuss how structural effects, water content and temperature facilitates proton transport through the Grotthus-like hopping mechanism. These data will also be used to validate the modeling predictions of our collaborators and to synthesize optimal fluorinated phosphonic acid containing ionomers.