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The performance of sustainable polymers can be modified and enhanced by incorporating functional groups in the backbone of the polymer chain that increases intermolecular interactions, thus impacting the thermal properties of the material. However, in-depth studies on the role of intermolecular interactions on the crystallization of these polymers are still needed. This work aims to ascertain whether incorporating functional groups able to induce intermolecular interactions can be used as a suitable systematic strategy to modify the polymer thermal properties and crystallization kinetics. Thus, amide and additional ester groups have been incorporated into aliphatic polyesters (PEs). The impact of intermolecular interactions on the melting and crystallization behavior, crystallization kinetics, and crystalline structure has been determined. Functional groups that form strong intermolecular interactions increase both melting and crystallization temperatures but retard the crystallization kinetics. Selecting appropriate functional groups allows tuning the crystallinity degree, which can potentially improve the mechanical properties and degradability in semicrystalline materials. The results demonstrate that it is possible to tune the thermal transitions and the crystallization kinetics of PEs independently by varying their chemical structure. 

Sustainable gas barrier materials, such as polyglycolide, poly(l-lactide), and poly(ethylene 2,5-furandicarboxylate) are important alternatives to traditional plastics used for packaging where low gas permeability is beneficial. However, high degrees of crystallinity in these materials can lead to undesirably low material toughness. We report poly(ester–amide)s derived from glycolide and diamines exhibiting both high toughness and desirable gas barrier properties. These sustainable poly(ester–amide)s were synthesized from glycolide-derived diamidodiols and diacids. To understand the structure–property relationships of the poly(ester–amide)s, polymers with different numbers of methylene groups were compared with respect to thermal, mechanical, and gas barrier properties. As the number of methylene groups between ester groups increased in the even-numbered series, the melting temperature decreased and oxygen permeability increased. We also found that these polymers are readily degradable under neutral, acidic, and basic hydrolytic conditions. These high-performance poly(ester–amide)s are promising sustainable alternatives to conventional gas barrier materials. 

The origin of melt memory effects associated with semicrystalline polymers and the physical parameters involved in this process have been widely studied in the literature. However, a comprehensive understanding of the role of intermolecular interactions on melt memory is still being developed. For this purpose, we have considered aliphatic polyesters and we have incorporated amide and additional ester groups. Inserting these additional functional groups, the strength of the intermolecular interactions increases widening the melt memory effect. Not only the presence of the functional groups but also the position of these groups in the repeating unit plays a role in the melt memory effect as it impacts the strength of the intermolecular interactions in the crystals. The study of the effect of intermolecular interactions has been extended to successive self-nucleation and annealing thermal fractionation experiments to explore for the first time the role of intermolecular forces on the fractionation capacity of linear polymers. We demonstrated that intermolecular interactions act as intrinsic defects interrupting the crystallizable chain length, thus facilitating thermal fractionation. Overall, this work sheds light on the role of intermolecular interactions on the crystallization behavior of a series of aliphatic polyesters.