Big spherulite structure and high crystallinity are the two main drawbacks of poly(butylene succinate) (PBS) and hinder its application. In this work, a new type of copolyester poly(butylene succinate-co-butylene acetylenedicarboxylate) (PBSAD) is synthesized. With the incorporation of acetylenedicarboxylate (AD) units into PBS chains, the crystallization temperature and crystallinity are depressed by excluding AD units to the amorphous region. In contrast, the primary nucleation capability is significantly strengthened, without changing the crystal modification or crystallization kinetics, leading to the recovery of total crystallization rate of PBSAD under the same supercooling condition. The existence of specific interaction among AD units is found to be crucial. Although it is too weak to contribute to the melt memory effect at elevated temperature, the interaction continuously strengthens as the temperature falls down, and the heterogeneous aggregation of AD units keeps growing. When the aggregating process reaches a certain extent, it will induce the formation of a significant amount of crystal nuclei. The unveiled nucleation mechanism helps to design PBS copolymer with good performance.

Co-crystallization plays a crucial role in the integration and regulation of thermal and mechanical properties in polymer blends, but the poor compatibility of the components in the crystal phase has always been a major obstacle to co-crystallization, which puts forward stricter requests for linkage and interaction between different entities. On the basis of the hydrogen-bonding interaction that can promote chain stacking and thus improve miscibility, we propose that crystalline/crystalline blends of 2-ureido-4[1H]-pyrimidinone (UPy)-functionalized poly(butylene succinate) and poly(butylene fumarate) (PBS-UPy/PBF-UPy) where UPy groups with quadruple hydrogen-bonding interaction are employed to connect different chain ends, could inhibit phase separation and improve co-crystallization. PBS-UPy/PBF-UPy blends exhibit complex component-dependent and cooling-rate-dependent co-crystallization behavior. A high level of co-crystallization occurs in the range of PBS-UPy-rich fractions, and the proportion could approach over 98% under optimized conditions with the aid of UPy quadruple hydrogen bonds interaction. This work enriches the understanding of co-crystallization in crystalline/crystalline polymer blends and provides more possibility for the design of structures and properties of polymer materials.

Extended-chain crystals (ECCs) of poly(butylene succinate) (PBS), featuring highly ordered molecular chains and exceptional thermal stability with a melting point 25 °C higher than conventional folded-chain crystals, demonstrate remarkable potential as nucleating agents for PBS crystallization. The incorporation of 5 wt% ECCs leads to a 12 °C increase in crystallization temperature and reduces crystallization half-time by 88% at 98 °C. Most significantly, self-nucleation studies reveal an unprecedented expansion of Domain II temperature window (∆T = 30 °C), exhibiting enhanced melt memory effects and a broadened processing window. Rheological investigations uncover the formation of unique intermolecular interactions in the melt, evidenced by non-terminal viscoelastic behavior and reduced loss tangent at elevated temperatures, with complementary evidence from higher ECC loadings confirming these findings. This local ordered structure exhibits remarkable thermal stability, persisting even above the melting point through specific intermolecular interactions, leading to the melt memory effect. These findings establish a new paradigm for nucleation control in biodegradable polyesters and provide molecular design strategies for high-performance sustainable materials.