Solvent-Free Iodination\nof Polyethylene via Twin-Screw\nExtrusion: A Scalable Approach

This study presents a novel, solvent-free approach for\nthe iodination\nof polyethylene (PE) using twin-screw extrusion under mild conditions.\nThe iodination process, typically challenging due to the inertness\nof PE, was successfully carried out using iodoform (CHI<sub>3</sub>) as the iodine source and NaOH as the initiator, all at a low reaction\ntemperature of 106 °C. Initial optimization using <i>n</i>-hexadecane as a model compound yielded efficient monoiodination,\nwhich was then extended to PE, achieving iodine incorporation levels\nof up to 23 wt %. The process was further applied to isotactic polypropylene\n(<i>i</i>PP), reaching iodine contents of approximately\n22 wt %. The resulting iodinated polymers were characterized using <sup>1</sup>H NMR, SEC, FT-IR, TGA, and XPS, confirming successful iodine\nincorporation and the absence of polyolefin chain cleavages. Thermal\nanalysis revealed significant changes in crystallinity and melting\ntemperatures, directly correlated with the iodine content, especially\nfor PE. This scalable, environmentally friendly method opens new avenues\nfor polyolefin functionalization, enhancing their potential in advanced\nmaterials, including biomedical imaging and diagnostics, where iodine’s\nhigh atomic number improves radiopacity, as well as flame-retardant\npolymers and polymers with improved coating and adhesion properties\n(Lex et al. Sci. Rep. 2020, 10, 1508−8900; Kim Elsevier 2017, 135–155).