Design And Preparation Of Low Dielectric Constant Poly(Aryl Ether Kotone)s And Their Composites

High performance polymers have attracted considerable attention over the pastdecade owing to the increased demands for their use as replacements for metals orceramics. Poly（aryl ether ketone）s （PAEKs） are a class of important high-performancearomatic polymers with excellent mechanical properties, good solvent resistance,size-accuracy, electrical characteristics, and superior thermal stability, which possesssome potential applications in aerospace, automobile, electronics, and other hightechnology fields. In recent years, there has been a continuous demand forhigh-temperature materials in microelectronic devices. Therefore, aromatic polymerswith low dielectric constants, high thermal stabilities and good mechanical propertieshave been widely investigated. In the past decade, a number of techniques have beenexplored for the preparation of low dielectric constant high performance materials,including （i） introduction of voids into polymer matrix by foaming processes;（ii）incorporation of fluorinated substituent into polymers; and （iii） embedment ofnanoporous inorganic or organic particles into polymers. The low dielectric constantPAEKs obtained by first methods, sometimes, exhibit poor thermal and mechanicalproperties. So, we focus on the other two methods to prepare low dielectric constantPAEKs in our manuscript. First, a series of novel adamantane-based co-poly（arylether ketone）s with low dielectric constants （PAEK-CF₃-Ad） were prepared bypost-amidation reaction of co-poly（aryl ether ketone）s containing （3-trifluoromethyl）phenyl and carboxyl groups （PAEK-CF₃-COOH） with4-adamantyl aniline（NH₂-Ph-Ad）. To compare with the preparation of adamantane containing PAEKs bydirectly polymerization of adamantyl-substituted monomers, this side chain grafting method could avoid some problems, such as the high polymerization temperature andthe difficult polymerization process of adamantyl-substituted monomers. Moreover,the dielectric, thermal, and mechanical properties of the synthesized PAEK-CF₃-Adwere characterized using a precision impedance analyzer, differential scanningcalorimetry, thermal gravimetric analyzer, and universal tester, respectively. Theresults indicate that PAEK-CF₃-Ad films had the low dielectric constants ranged from2.65to2.33at1MHz due to the introduction of the adamantyl groups. Besides, thesynthesized PAEK-CF₃-Ad copolymers exhibited good thermal and mechanicalproperties.Then, A material with low dielectric constant was produced using nanoparticlephosphotungstic acid （PWA） modified by the silane coupling agentγ-aminopropyltriethoxysilane （KH-550） dispersed in a poly（aryl ether ketone）containing （3-trifluoromethyl） phenyl side groups （FPEEK） matrix synthesized with（3-trifluoromethyl） phenyl hydroquinone （3FHQ） and4,4’-difluorobenzophenone（DFB）. The material was fabricated using solution-blending. Moreover, the dielectric,thermal, and mechanical properties of this material were characterized using aprecision impedance analyzer, thermal gravimetric analyzer, and universal tester,respectively. The results indicate that modified PWA （m-PWA）/FPEEK compositesshow obvious improvement in the dielectric properties compared to unmodified PWA（p-PWA）/FPEEK composites. When the PWA contant reached10wt%, the dielectricconstant of （m-PWA）/FPEEK composites could achieve as low as2.28（1MHz）. Thisshould be attributed to the good dispersion and compatibility of m-PWA in FPEEK, asproven by scanning electron microscope （SEM） and wide-angle X-ray diffraction（WAXD）. Besides, m-PWA/FPEEK composites also exhibited the relatively goodthermal and mechanical properties. In addition, the novel ultra low dielectric constantpoly（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 thepresence the silane coupling agent γ-aminopropyltriethoxysilane （KH-550） wereprepared and characterized. The chemical structures of the PWA/PEEK-CF₃-COOH hybrid films were confirmed by FT-IR spectroscopy and1H-NMR. The analysis ofwide-angle X-ray diffraction （WAXD） indicated that the PWA clusters could not formcrystalline structures in the PEEK-CF₃-COOH matrix, and the investigation of thescanning electron microscopy （SEM） and energy dispersive spectrometer （EDS）（W-mapping） revealed that the PWA particles were well dispersed in thePEEK-CF₃-COOH matrix with nanoscale. The influence of the incorporation of PWAparticles by side chain grafting reaction on the properties of PEEK-CF₃-COOH wasstudied. The dielectric constants of the PWA/PEEK-CF₃-COOH hybrid films wereremarkably lower than that of neat PEEK-CF₃-COOH film and the lowest value oftheir dielectric constant could achieve as low as1.96（1MHz） when the content ofgrafted PWA reached10wt%. Meanwhile, the hybrid films still retain the excellentthermal and mechanical properties as well as the good transparency.Further, a serious of novel ultra low dielectric constant soluble organic-inorganicnanocomposites in which nanoscale octa-aminophenyl polyhedral oligomericsilsesquioxanes （NH₂-POSS） were covalently linked onto the fluoropoly（ether etherketone）s （PEEK-CF₃-COOH） were prepared and characterized. The chemicalstructures of the polymer matrix and nanocomposites were confirmed by1H NMR andFT-IR spectra. The analysis of wide-angle X-ray diffraction （WAXD） and X-rayphotoelectron spectra （XPS） indicated that the POSS clusters were successfullyincorporated into the polymer matrix and the homogeneous dispersion of POSS cagesin the polymer matrix was evidenced by scanning electron microscopy （SEM） andenergy dispersive spectrometer （EDS）（Si-mapping）. Further more, the influence ofthe incorporation of POSS particles on the properties of nanocomposites wasinvestigated. The dielectric constants of the organic-inorganic nanocomposites weredrastically reduced relative to neat PEEK-CF₃-COOH films and the dielectric constantcould achieve as low as1.71（1MHz）. Besides, the thermal and mechanical propertiesof the nanocomposites were significantly improved by incorporation of NH₂-POSSmoieties.Finally, by Ullmann coupling reaction, ultra low dielectric constant solubleorganic-inorganic nanocomposites in which nanoscale octa-aminophenyl polyhedral oligomeric silsesquioxanes （NH₂-POSS） were covalently linked onto the iodinecontaining fluoropoly（ether ether ketone）s （PEEK-CF₃-I） were prepared. Thechemical structures of the polymer matrix and nanocomposites were confirmed by1HNMR and FT-IR spectra. The analysis of wide-angle X-ray diffraction （WAXD） andX-ray photoelectron spectra （XPS） indicated that the POSS clusters were successfullyincorporated into the polymer matrix and the homogeneous dispersion of POSS cagesin the polymer matrix was evidenced by scanning electron microscopy （SEM） andenergy dispersive spectrometer （EDS）（Si-mapping）. Moreover, the influence of theincorporation of POSS particles on the properties of nanocomposites was investigated.The dielectric constants of the organic-inorganic nanocomposites were furtherdrastically reduced relative to neat PEEK-CF₃-I films and the dielectric constant couldachieve as low as1.64（1MHz）. Besides, the nanocomposites also displayed excellentthermal and mechanical properties.