High molecular weight polyesterscontaining thermally curable benzoxazine units in the main chain have been synthesized. For this purpose, first the diol functional monomer is synthesized through the Mannich and subsequent ring closure reactions of bisphenol‐A, paraformaldehyde, and 5‐amino‐1‐pentanol. Polycondensation of the resulting benzoxazine and pyromellitic dianhydride or 4‐4′‐(hexafluoroisopropylidene)