Effects of the Composition Ratio, Eosin Addition, and c Irradiation on the Dielectric Properties of Poly(vinyl Alcohol)/Glycogen Blends F. H. Abd El-Kader, 1 S. A. Gaafar, 2 K. H. Mahmoud, 1 S. I. Bannan, 2 M. F. H. Abd El-Kader 2 1 Department of Physics, Faculty of Science, Cairo University, Giza, Egypt 2 Department of Biophysics, Faculty of Science, Cairo University, Giza, Egypt Received 1 August 2007; accepted 17 January 2008 DOI 10.1002/app.28566 Published online 16 July 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The dielectric relaxation spectra of various poly(vinyl alcohol) (PVA)/glycogen blends and irradiated blend samples with 70 wt % PVA content that were undoped and doped with eosin were measured in extended temperature (30–1608C) and frequency (1 kHz to 1 MHz) ranges. Dielectric relaxation spectroscopy sepa- rates different molecular groups of a repeating unit of a polymer with respect to the rate of its orientation dynam- ics. In the high-temperature range (>1008C), the r relaxa- tion, which is associated with the hopping motion of ions in the disordered structure of the biopolymeric material, can be measured. The electric dipole moment and the acti- vation energy of the glass-transition temperature relaxa- tion process were calculated. V V C 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 1281–1288, 2008 Key words: activation energy; amorphous; barrier; biomaterials; blending INTRODUCTION Dielectric spectroscopy is sensitive to the intensity and velocity of orientational changes of mean dipole moments within a small volume unit in substances exposed to an electric field. It provides experimental results that concern the mobility of polymers bearing dipolar regions or dipolar side groups. It is quite common in the dielectric spectroscopy of natural and synthetic polymers to distinguish between the primary relaxation (a relaxation) and several secondary relaxations. The a relaxation is related to the glass transition, and it is observed in the temperature range above the glass-transition temperature (T g ). The secondary relaxation processes observed in the range of temperatures below the glass transition (sub-T g ’s) are related either to the local main-chain dynamic (b relaxation) or to differ- ent side-group motions (c relaxation). It was found recently 1–3 that there is an additional dielectric relaxation process called r relaxation in the higher temperature range (80–1808C) for amorphous solid systems, polysaccharides, and other polymers, which obviously cannot be assigned to any molecular dipo- lar group orientation. This process is associated with the hopping motion of ions in the disordered struc- ture of the polymeric material. It is strongly related to the direct-current (dc) conductivity of the poly- meric system. The aim of this study was to perform a compre- hensive study of the influence of the addition of eosin and c irradiation on the dielectric properties and associated relaxation phenomena of PVA/glyco- gen compositions. We undertook a systematic inves- tigation of the dielectric constant (e 0 ) and dielectric loss factor (e 00 ) in the frequency range 1 kHz to 1 MHz and in the temperature range 30–1608C. EXPERIMENTAL Weighed amounts of PVA granules were dissolved in a mixture of distilled water and ethanol with a 4 : 1 ratio. Also, weighed amounts of glycogen were dissolved in distilled water at room temperature. A solution of PVA and glycogen were mixed together with different weight percentages of PVA/glycogen (100/0, 85/15, 70/30, 50/50, 30/70, and 0/100 w/w) with a magnetic stirrer at 508C. Thin films of appro- priate thickness ( 0.01 mm) were cast onto stainless steel Petri dishes and then dried in air at room tem- perature for about 6 days until the solvent was com- pletely evaporated. The obtained glycogen film was brittle; therefore, it was used as a powder in the form of pellets with an approximate thickness of 0.136 cm for these studies. Films were cut into slab pieces and prepared to fit the cells of the measuring techniques. Journal of Applied Polymer Science, Vol. 110, 1281–1288 (2008) V V C 2008 Wiley Periodicals, Inc. Correspondence to: K. H. Mahmoud (cairouni1@yahoo. com).