Copolymers of vinylphosphonic acid with zirconium vinylphosphonate have been synthesized via free radical polymerization from immiscible mixtures into amorphous, transparent, water stable, and flexible membranes. Ion exchange capacities range from 6 to 10 mequiv/g, corresponding to equivalent weights well below 200 g/mol. A 20 wt % loading of the vinyl zirconium phosphonate comonomer is XRD amorphous. It is shown that 1.5 of the 2 protons in the beginning acidic groups are dissociated in the 20 wt % VZP loaded ionomer, allowing these materials to have high proton conductivities, up to and exceeding 0.1 S cm(-1) at 80 degrees C and 80% RH. Water uptake measurements show very little swelling of the material below 70% RH land ca. 1 water per proton at low RH. Proton conductivity under dry conditions, roughly 0.05 S cm-1 with a lambda < 1, indicates that he material conducts protons under limiting hydration conditions and strongly implicates transport by a pure Grotthuss mechanism.