Well-Defined Chain-End Functionalized Polyethylenes with Different Macromolecular Architectures

This study reports the synthesis of a wide library of α,ω-dihydroxy, ω-hydroxy (linear and 3-arm star), and ω-amine functionalized, as well as nonfunctionalized polyethylenes (linear and 3-arm star) via diimide hydrogenation of the corresponding polybutadiene precursors. All polyethylenes were synthesized using anionic polymerization high-vacuum techniques followed by suitable postpolymerization reactions and hydrogenation. Molecular characterization confirmed low 1,2-microstructures in the polybutadiene precursors, resulting in linear low-density polyethylene (LLDPE)-like architectures, after hydrogenation. Additionally, perfectly linear ω-hydroxy polymethylene (equivalent to polyethylene) samples, resembling high-density polyethylene (HDPE) structures, were synthesized via polyhomologation. Thermal analysis and X-ray diffraction measurements showed reduced crystallinity in the functionalized samples, likely due to hydrogen-bonding effects that disturb the crystalline packing. In contrast, the polyethylene synthesized via polyhomologation exhibited higher crystallinity values, resembling the structure of high-density polyethylene (HDPE). These findings underscore the influence of functional groups on polyethylene properties, motivating future studies on their thermal and dielectric behavior.