Zhengfeng Zhu, Sai Xu, Song Liu, Chuang You, Guisong Wang, Huiyu Wang, Jun Guan, Shaohua Zeng
The intrinsic brittleness of epoxy resin (EP) severely limits its use in applications requiring both strength and toughness. Herein, methoxy polyethylene glycol-functionalized carbon nanotubes (mPEG-CNTs) were prepared via an in-situ grafting strategy, leveraging the outstanding structural characteristics of carbon nanotubes (CNTs). The obtained mPEG-CNTs were subsequently incorporated into an epoxy matrix to fabricate mPEG-CNTs-filled composites. The effects of mPEG-CNTs on the structure and properties of epoxy composites were systematically investigated. At an optimal loading of 1.25 wt.%, the tensile strength, tensile toughness, and Young’s modulus increased by 30.7%, 61.27%, and 28.57%, respectively, compared with neat EP; furthermore, the storage modulus at 30°C and 170°C increased by 8.8% and 77.10%, respectively, demonstrating improved rigidity and thermal stability. Microstructural analysis confirmed the uniform dispersion of mPEG-CNTs within the epoxy matrix and the formation of a semi-interpenetrating polymer network (semi-IPN) at the filler/matrix interface, strengthening interfacial interactions. The composites also exhibited an increased dielectric constant while maintaining low dielectric loss over a wide frequency range. The semi-IPN structure suppressed conductive leakage pathways and limited dielectric loss despite enhanced interfacial polarization. These results indicate that the mPEG-CNTs-induced interfacial architecture contributes to a balanced enhancement of mechanical, thermal, and dielectric properties.