In the presence of one equivalent of acid, m‐phenylenediamine and 2‐methyl m‐phenylenediamine react with pyridine‐3 aldehyde with C alkylation to produce linear polymers, poly(4,6‐R‐methylene m‐phenylenediamine) and poly(4,6‐R‐methylene 2‐methyl m‐phenylenediamine). These were characterized by UV, IR, and NMR spectroscopy. Comparison with model compounds confirmed the above structures. A secondary reaction noted at 25°C and higher for the polymer was the oxidative coupling of two neighboring aromatic diamines to produce substituted 2,7‐diamino acridine groups along the chain.