DIELECTRIC CHARACTERISTICS OF NOVEL HYBRID MATERIALS CONSISTING OF FUNCTIONAL BLOCK COPOLYMERS AND METAL OXIDE NANOPARTICLES AT TEMPERATURE AND FREQUENCY VARIATION Cristina BRATESCU 1 , Ramona BURLACU 1 , Romeo CIOBANU 1 , Theodora KRASIA-CHRISTOFOROU 2 , Vasilica Alina NEAMTU 1 1 “Gheorghe Asachi” Technical University of Iaúi, România, Faculty of Electrical Engineering, cbratescu@ee.tuiasi.ro 2 University of Cyprus, Nicosia, Cyprus, Department of Mechanical and Manufacturing Engineering Abstract  Most polymeric materials are characterized by low surface energies; therefore, in order for a polymer to be able to adhere efficiently onto a metallic/metal-oxide surface, the development of specific polymer-metal interactions is required. Such interactions include among others hydrogen- or covalent bonding, dipolar and electrostatic interactions, and require the presence of specific functional sites on the polymer backbone. The resulting organic-inorganic hybrid materials are particularly interesting, since they inherit properties of the polymer (such as good mechanical performance, formation of well-defined nano-morphologies) and of the metals (electro- magnetic, thermal, and optical properties). To further understand the dielectric behavior of nano- conductive– polymer composites, this experimental work reports the trends of dielectric permittivities and tan delta (loss tangent) of polymer/metal hybrid nanomaterials: LauMA-b-AEMA/Pd and LauMA-b-AEMA/Au and OA.Fe3O4 at temperature and frequency variation using a system for automated dielectric spectroscopy, given by Novocontrol GmbH, Germany. The dielectric properties were measured in the frequency range from 1 to 10 6 Hz and a temperature range of 35°C - 70°C for all samples. Keywords: block copolymers, polymer/metal hybrid nanomaterials, dielectric properties. 1. INTRODUCTION Electromagnetic Interference (EMI) and Electromagnetic compatibility (EMC) are becoming important issues in the design of novel high-speed transmission networks and producing safe and sure equipment, with fast growing market at more than 5- 7% per year. The need for novel electromagnetic active materials and technological solutions - mainly starting from nano/micro-scale concepts is related to urgent and large scale implementation of Council Recommendation 1999/519/EC on the limitation of exposure of the general public to electromagnetic fields and also Directive 2004/40/EC on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (EMFs), which will determine an explosion in the next 3-5 years of the actual EMC/EMI market. [1] The present situation of European industry in the EM field consists in the transition from intensive use of resources to high added value material production, by implementing new materials with improved properties, new functionalities, and new applications according to new environmental requirements. [2] Some actual technical solutions developed in the last 5 years, but still unsuccessfully promoted on market are as follows: - composites with carbon nanotubes, blended with epoxy resin for e.g. composite radar absorbing materials (RAM). The polymer composite paste technology is available, i.e. to be put into dedicated metal plates to form a prototype. Carbon nanotubes may be characterized by TEM, and radar absorbing properties may be detected by a RAM measuring system of arch method reflectivity. The double absorbing peaks of the sample with mm thickness may be obtained when the carbon nanotubes and epoxy resin are in a ratio of e.g. 1:100. The material has unfortunately low features reproducibility. - nanocomposites of magnetic materials using e.g. Į- Fe/C, Fe 2 B/C or Fe 1.4 Co 0.6 B/C, nowadays used for other purposes, but intended to be adaptable for EM applications. They may be made as complex composites prepared by mechanically grinding Į-Fe, Fe 2 B, or Fe 1.4 Co 0.6 B with amorphous carbon [C(a)] powders. Complex permittivity, permeability, and electromagnetic wave absorption properties of such resin compacts containing e.g. 40-vol % composite powders of Į-Fe/C(a), Fe 2 B/C(a), and Fe 1.4 Co 0.6 B/C(a) may be adapted for conventional reflection/transmission technique, for dedicated applications in ranges of 4.3-8.2 GHz (G band), 7.5- 16.0 GHz (X band), and 26.5-40 GHz. The material has unfortunately low reliability. - conductive polyaniline/iron carbonyl powder composite material, prepared based on conductive Annals of the University of Craiova, Electrical Engineering series, No. 35, 2011; ISSN 1842-4805 _________________________________________________________________________________________________________________ 59