Poly(styrene-co-styrenesulfonic acid) copolymers containing 2-10 mol % acidic units were mixed in stoichiometric amounts of interacting groups with poly(styrene-co-(4-vinylpyridine)) copolymers containing 2-10 mol % basic units. FTIR spectroscopy revealed that ca. 80-90% of the pyridine units in the blend were protonated, with the pyridinium ions II-bonded to the anion. An FTIR temperature study indicated that the pyridinium units were involved in an equilibrium involving the H-bonded pyridinium/sulfonate ion pair and most likely the II-bonded but nonionic acid/base pair. Previously reported mechanical property measurements were interpreted in light of these results.