AbstractHigh molecular weight polyphthalamides melting above 325°C. were prepared from piperazine, 2‐methylpiperazine, and 2,5‐dimethylpiperazine by interfacial polycondensation. The melt temperatures and decomposition points of the polyphthalamides, polyisophthalamides, and polyterephthalamides of the above diamines were determined. Only low molecular weight polyphthalamides were obtained from primary diamines. Copolymers of high molecular weight were prepared from piperazine and 2,5‐dimethylpiperazine with phthaloyl chloride containing various proportions of terephthaloyl chloride, isophthaloyl chloride, adipoyl chloride, or ethylene bis(chloroformate).