Dielectric and mechanical properties of diglycidyl ether of bisphenol a modified by a new fluoro‐terminated hyperbranched poly(phenylene oxide)

Diglycidyl ether of bisphenol A (DGEBA)/fluoro‐terminated hyperbranched poly(phenylene oxide) (FHPPO) composites with improved mechanical and dielectric performances were prepared by blending a FHPPO with DGEBA. The low‐polarity building blocks, abundant fluorinated terminal groups, and the inherent free volume brought by FHPPO efficiently lowered the dielectric constant and the dissipation factor. The free volumes of the cured DGEBA/FHPPO composites, which were quantified by positron annihilation lifetime spectroscopy, increased with the FHPPO loading. The moisture absorption of composites also decreased after the introduction of FHPPO due to the hydrophobicity of fluorinated substituents. Dynamic mechanical analysis tests and scanning electron morphology revealed that FHPPO phase separated from the composites during the curing process. The average diameter of dispersed FHPPO particles increased proportionally with the FHPPO loading. Composites with dispersed particle size of around 150 nm showed the best comprehensive mechanical performance. In addition, incorporation of FHPPO, which has lots of aromatic structures, into DGEBA also increased the thermal stabilities. POLYM. COMPOS., 34:1051–1060, 2013. © 2013 Society of Plastics Engineers