Materials Chemistry and Physics 123 (2010) 9–12 Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Materials science communication Dielectric characteristics of poly(N-vinylcarbazole) and its nanocomposites with ZnO and acetylene black Debanjana Ghosh a , Pinki Saha Sardar a , Mukul Biswas a,∗ , Anup Mondal b , Nillohit Mukherjee b a Department of Chemistry and Biochemistry, Presidency College, Kolkata 700073, India b Department of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah 711103, India article info Article history: Received 18 July 2009 Received in revised form 29 March 2010 Accepted 16 April 2010 Keywords: Poly(N-vinylcarbazole) ZnO Acetylene black Nanocomposites Dielectrics properties Polarization abstract Dielectric constant and dielectric loss parameters of poly(N-vinylcarbazole) homopolymer and several nanocomposites of poly(N-vinylcarbazole) with ZnO were studied as a function of frequency. In the low frequency range (0–20 kHz) the dielectric constant values of the base polymer varied from ∼30 to ∼2, and the same for the composite varied from 8500 to 2000 (4.54), 5000 to 1000 (2.63) and 2000 to 500 (1.17), the figures in parenthesis denoting the ratio of ZnO:PNVC in the nanocomposites. Likewise, dielectric loss parameters were found to be (7–10 × 10 -3 ) for the homopolymer and 4.0, 2.5 and 1.25 for the three PNVC–ZnO composites respectively. Notably, a mechanical mixture of ZnO and PNVC (1.17) exhibited much lower dielectric constant (400–25) and loss parameters (0.14–0.065). These features imply polar- ization was differently affected depending on factors such as grain size and grain-boundary interfaces being formed in these systems. Tan ı–temperature variation for the composites revealed the occurrence of a maximum between 60 and 70 ◦ C. These features signified dipole group loss in the composite. Dielec- tric constant of a conducting nanocomposite of poly(N-vinylcarbazole) with acetylene black revealed very low negative value tending to zero at high frequency. © 2010 Published by Elsevier B.V. 1. Introduction Polymer based nanocomposites with high dielectric param- eters have been receiving increasing research attention during recent times for potential applications in electronic devices at high operating frequencies. A variety of polymer-inorganic hybrid composite systems have been studied extensively during the past ten years. Composites of lead zirconate titanate/polyvinylchloride (PVC) [1], barium titanate/PVC [2], barium titanate/cyanoresin polymers [2], Fe 3 O 4 /polypyrrole (PPY) [3] and TiO 2 /polyaniline(PANI) [4], TiO 2 /polymethylmethacrylate(PMMA) [5], TiO 2 /poly(phenylenevinylene) (PPV) [6] have been investi- gated as high K materials. Interestingly, composites of low density polyethylene with ZnO–nZnO composites [7] show rather low dielectric constant values (2.5–4.58). Poly(N-vinylcarbazole) (PNVC) is a polymer well characterized [8] in regard to its high thermal stability, photoconductivity and interesting optoelectronic characteristics [8]. PNVC exhibits very low dielectric constants e.g. ∼3and loss factor of ∼10 -3 over a wide range of temperature and frequency [9]. These properties along ∗ Corresponding author at: Department of Chemistry, Presidency College, 86/1, College Street, Kolkata 700073, West Bengal, India. Tel.: +91 9051340721. E-mail addresses: mukulbiswas007@gmail.com, mukul biswas@vsnl.net (M. Biswas). with those mentioned above make the polymer suitable for many industrial applications. However, in view of the low dielectric con- stant of PNVC homopolymer it was felt that the scope of application of this polymer could be enhanced if PNVC could be appropriately modified to yield a high dielectric constant material. To convert PNVC into a high K material we selected to prepare a composite of the polymer with a nanosized metal oxide, keeping in view that many of such polymer based hybrid materials usually exhibit high dielectric constant values. As described above in such studies mostly ferroelectric oxides such as BaTiO 3 , TiO 2 or Fe 3 O 4 in the nanometer particle sizes range have been used to prepare nanocomposites with polymers like PVC, PPY, PANI and PMMA. In our studies nanosized ZnO was used and the PNVC–ZnO nanocom- posites was prepared by a recently published procedure by Ghosh and Biswas [10]. We realized attractively high dielectric constant and dielec- tric loss values for this composite in contrast to those for PNVC homopolymer. Another interesting feature of these systems is that PNVC–ZnO composite is non-conducting while the reported PANI/PPY/ferroelectric oxide composites with high K values are semi conductors ( = 10 -3 to 10 -5 S cm -1 ). In this background we also examined the dielectric characteristics of a conducting nanocomposite (2–8 × 10 -2 S cm -1 ) of PNVC with acetylene black (AB) prepared and characterized by Biswas and co-workers [11]. In sharp contrast to the dielectric behavior of PNVC–ZnO, PNVC–AB composite exhibited negative dielectric constant values tending 0254-0584/$ – see front matter © 2010 Published by Elsevier B.V. doi:10.1016/j.matchemphys.2010.04.019