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

The number of methylene groups between strongly interacting\nfunctional\ngroups within polymer repeating units induces even–odd effects\non thermal and mechanical properties. However, detailed studies correlating\nthe even–odd effect with structural changes are still lacking.\nIn this work, we establish correlations between the structure and\nthermal properties of poly(ester amide)s containing long alkyl chain\nlengths. The even–odd effect impacts the thermal properties,\nincluding the melting temperature and crystallinity degree. It influences\nthe spherulitic morphology of poly(ester amide)s, controlling the\nappearance of banding. We demonstrate that even–odd effects\nin poly(ester amides)s persist even with 27 CH<sub>2</sub> groups\nwithin the repeating unit, an effect due to strong hydrogen bonds\ncaused by the amide groups. Our X-ray studies reveal that the even–odd\neffect originates from changes in the crystalline structure of the\nmaterials. This work helps elucidate the role of strong intermolecular\ninteractions (i.e., hydrogen bonding) on the even–odd effect\nin long-chain poly(ester amides).