A series of novel fully aromatic poly(arylene ether sulfone)s that contain 1,3,5-s-triazine groups were synthesized by the reaction of triazine-containing bisphenols with bis(4-fluorophenylsulfone) to study the effects of branching groups on solubility as well as thermal and mechanical properties. Polymers had inherent viscosities from 0.43 to 1.10 dL/g, thermal stabilities >500 degrees C in air, glass transition temperatures from 136 to 289 degrees C, and good film forming abilities. The polymer with pendant diphenylamine groups on the triazine ring were further investigated for use in proton exchange membranes based on solubility, thermo-oxidative stability, and case of monomer synthesis. A series of copolymers made from 4,6-bis(4-hydroxyphenyl)-N,N-diphenyl-1,3,5-triazin-2-amine and 4,4'-biphenol were sulfonated with chlorosulfonic acid to achieve ion exchange capacities up to 2.62 mmol/g. The homopolymer was sulfonated exclusively on the diphenylamine branch and had the highest proton conductivity (0.11 S/cm at 95 degrees C and 100% relative humidity), even though it had the lowest water uptake and ion exchange capacity. Unsulfonated polymers and sulfonated copolymers showed little uptake of phosphoric acid. However, the sulfonated homopolymer with pendant diphenylamine groups had a 200-250 wt % uptake when soaked in 85% H3PO4 at 90 degrees C, but the proton conductivity of this polymer was lower than the hydrated polymer without H3PO4 added.