Miyeon Lee

Polyimide (PI) films are widely utilized in advanced engineering applications due to their excellent thermal stability, mechanical integrity, and electrical insulation. Despite these advantages, their intrinsic brittleness limits broader structural implementation. In this work, carbon nanotubes (CNTs) were non‐covalently functionalized using poly(amic acid) salt (PAS), a precursor polymer structurally similar to PI, to enhance filler dispersion and interfacial compatibility. The PAS modification markedly improved CNTs distribution within the PI matrix, leading to strengthened interfacial interactions and more efficient stress transfer. Mechanical testing showed that neat PI exhibited a tensile strength of 128.38 MPa, whereas incorporation of 0.5 wt% PAS‐CNT the increased the tensile strength to 214.44 MPa, corresponding to a 67.03% enhancement. The tensile modulus simultaneously increased from 4.41 to 7.96 GPa (80.50% improvement). Specifically, the PAS‐CNT/PI nanocomposites reached a conductivity of 168.55 S/m was achieved, which is approximately 7.86 times higher than that of pristine CNT/PI nanocomposites (21.43 S/m) at the same filler content (5 wt%). The improved conductivity enabled rapid and stable electrothermal heating under applied voltage. These results demonstrate that PAS‐assisted non‐covalent functionalization is an effective strategy for improving the dispersion and multifunctional performance of PI/CNT nanocomposites for electrothermal film applications.

The cover image is based on the Article Optically transparent and refractive thiol‐ene polymers containing cyclotriphosphazenes by Jeong‐Un Jin and Miyeon Lee et al., https://doi.org/10.1002/pol.20240386. image

A colorless, transparent thiol‐ene polymer network was developed that contains cyclic phosphazene units in the polymer chain. Hexakis (allyloxy) cyclotriphosphazene (HAP) was synthesized from the nucleophilic substitution reaction of phosphonitrilic chloride trimer and allyl alcohol. Thiol‐ene polymers (HAP‐SH) were successfully prepared without by‐products or the use of solvents through photopolymerization of the HAP and multithiol monomers with various functional group and flexible structures (e.g., 1,4‐butanedithiol (BDTH), 1,3,5‐benzenetrithiol (BTTH), trimethylolpropane tris (3‐mercaptopropionate) (TTMP) and pentaerythritol tetrakis (3‐mercaptopropionate) (PTTH)). The prepared HAP‐SH polymers showed sufficient thermal stability due to the high degree of cross‐linking. In addition, the HAP‐SH polymer films exhibited high optical transparency of over 90% in the visible region. The refractive indices of the HAP‐SH polymers measured at 637 nm were in the range of 1.5530–1.6344, and the Abbe number was calculated to be in the range of 34.5–47.1. These results are attributed to the structure of the cyclophosphazine and the polymer main chain containing aliphatic linkers with sulfur atoms. Another significant result was the transparency of the HAP‐SH polymer films in the mid‐infrared (MWIR) region. The thermal stability and excellent optical properties of the HAP‐SH polymers make them good candidates for application as a protective film for IR lenses, which are easily damaged by external factors.