The glass transition of three different polyesteramides, polyundecanamide‐undecanoates, polyundecanamide‐nonanoates, and polyundecanamide–p‐methylbenzoates has been investigated by differential thermal analyses. As the amino acid content in the polymer increases, the evolution of the glass transition temperature is strongly influenced by the comparative length and the stiffness of the two monomer units. The experimental data are discussed in terms of the disruption of a hydrogen‐bonded network in the amorphous regions of the copolymers.

The polycondensation of hydroxyamido acids of general formula HO‐R1‐CO‐NH‐R2‐COOH provides alternating polyesteramides only when R1 and R2 are alkyl groups. These aliphatic alternating polyesteramides, according to their structural high regularity, possess a more important content of interchain hydrogen bonds than the random copolymers. The higher melting point of the random copolymers is attributed to the heterogeneity of amide group partition in the chain. The existence of a benzyl group in the structure of the hydroxyamido acids reduces the polycondensation ability and the molecular weights of the products are low. These aromatic monomers are thermally degraded, p‐toluic acid evolving; ester and amide functions stoechiometric ratio is not maintained, but infrared and differential thermal analysis show that these aromatic polyestermides keep a reasonable structural regularity.