Crystallization of Well-Defined Chain-End Functionalized Polyethylenes with Varying Molecular Weights and Branching Architectures

High Resolution Image Download MS PowerPoint Slide Using a compositionally well-controlled set of materials, this work describes how chain-end chemistry and macromolecular architecture govern crystallization in semicrystalline polyethylene with variations in molecular weight, degree of short-chain branching (HDPE- vs LLDPE-like), topology (linear vs three-arm star), and end groups (nonfunctionalized, ω-hydroxy linear and 3-arm star, α,ω- dihydroxy, and ω-amine). Differential scanning calorimetry reveals a striking contrast where unbranched, HDPE-like linear polymethylenes with ω-hydroxy end groups show no self-nucleation or strong melt memory above T m 0 . Conversely, all short-chain-branched analogs exhibit strong melt memory that is amplified by hydrogen-bonding end groups and persists even after prolonged annealing in the melt. Isothermal crystallization kinetics slow markedly upon end-functionalization, yet collapse onto a single trend when isothermal measurement temperatures are scaled by the peak crystallization temperature, indicating that changes in nucleation dominate over supercooling effects. This observation is qualitatively corroborated by Avrami’s analysis of the kinetics. Long-range order was not detected in the melt and is consistent with a picture where associating chain-ends alter local packing and nucleation without creating a separate ordered phase. These results establish design rules for tuning crystallization via targeted end group interactions in branched polyethylenes and related semicrystalline polyolefins.