Microwave properties of poly(4,4′-diphenylene diphenylvinylene)

Abstract

4,4′-dibenzoylbiphenyl monomer was successfully synthesized via the Friedel–Crafts reaction with biphenyl and benzoylchloride as starting materials. The catalyst used was anhydrous aluminium chloride. 4,4′-dibenzoylbiphenyl monomer was characterized by GCMS, elemental analysis, FTIR and 13C and 1H NMR spectroscopies. The melting point of the monomer was 218.3–219.6 °C. Purity of the monomer was high as shown by the GCMS chromatogram. Poly(4,4′-diphenylene diphenylvinylene), PDPV was synthesized via McMurry coupling reaction by using 4,4′-dibenzoylbiphenyl, titanium tetrachloride and zinc dust as the monomer, catalyst and reducing reagent, respectively, in THF. PDPV was characterized by using DSC, TGA, GPC, FTIR and UV-VIS spectroscopies. Number average molecular weight, M n and weight average molecular weight, M w of PDPV were 1800 gmol −1 and 2300 gmol −1, respectively, with a polydispersity index of 1.28. Conductivity of PDPV at 298 K was 5.719×10 −5 S/cm as determined by using impedance spectroscopy. Reflection loss ( R L), shielding effectiveness ( SE), reflection power, transmission power and absorption power of PDPV within the frequency range of 0.3–13.5 GHz were calculated from complex scattering parameters that correspond to the reflection ( S ∗ 11 and S ∗ 22) and transmission ( S ∗ 12 and S ∗ 21) using a Hewlett Packard 8719D microwave vector network analyzer. In addition, ε′ r , ε″ r , μ′ r and μ″ r of PDPV from 0.3 to 13.5 GHz were identified. Most of incident microwave energy was transmitted (83.3%) and only 11.7 and 5.0% were absorbed and reflected by PDPV, respectively.