Ultra low dielectric constant hybrid films via side chain grafting reaction of poly(ether ether ketone) and phosphotungstic acid

The novel ultra low dielectric constant poly(ether ether ketone) hybrid films in which nanoscale phosphotungstic acid (PWA) clusters were grafted onto the side chains of poly(ether ether ketone) containing (3-trifluoromethyl) phenyl groups and carboxyl groups (PEEK–CF3–COOH) in the presence the silane coupling agent γ-aminopropyltriethoxysilane (KH-550) were prepared and characterized. The chemical structures of the PWA/PEEK–CF3–COOH hybrid films were confirmed by FT-IR spectroscopy and 1H-NMR. The analysis of wide-angle X-ray diffraction (WAXD) indicated that the PWA clusters could not form crystalline structures in the PEEK–CF3–COOH matrix, and the investigation of the scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) (W-mapping) revealed that the PWA particles were well dispersed in the PEEK–CF3–COOH matrix with nanoscale. The influence of the incorporation of PWA particles by side chain grafting reaction on the properties of PEEK–CF3–COOH was studied. The dielectric constants of the PWA/PEEK–CF3–COOH hybrid films were remarkably lower than that of the neat PEEK–CF3–COOH film and the lowest value their dielectric constant could achieve was as low as 1.96 (1 MHz) when the content of grafted PWA reached 10 wt%. Meanwhile, the hybrid films still retain the excellent thermal and mechanical properties as well as the good transparency.