Strong Hydrogen Bonds Sustain Even–Odd Effects in Poly(ester amide)s with Long Alkyl Chain Length in the Backbone

The number of methylene groups between strongly interacting functional groups within polymer repeating units induces even–odd effects on thermal and mechanical properties. However, detailed studies correlating the even–odd effect with structural changes are still lacking. In this work, we establish correlations between the structure and thermal properties of poly(ester amide)s containing long alkyl chain lengths. The even–odd effect impacts the thermal properties, including the melting temperature and crystallinity degree. It influences the spherulitic morphology of poly(ester amide)s, controlling the appearance of banding. We demonstrate that even–odd effects in poly(ester amides)s persist even with 27 CH 2 groups within the repeating unit, an effect due to strong hydrogen bonds caused by the amide groups. Our X-ray studies reveal that the even–odd effect originates from changes in the crystalline structure of the materials. This work helps elucidate the role of strong intermolecular interactions (i.e., hydrogen bonding) on the even–odd effect in long-chain poly(ester amides).