Effect of Molecular Weight on Dielectric Properties of Polyvinyl Alcohol Films Girish Joshi, 1 S. M. Pawde 2 1 Faculty of Engineering Physics, Watumull Institute of Technology, Worli, Mumbai, India 2 University Institute of Chemical Technology, Department of Applied Physics, Mumbai, India Received 3 April 2005; accepted 23 December 2005 DOI 10.1002/app.24062 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Impedance analysis is the best technique to reveal the microstructural details of the polymeric material. The dielectric polarization not only depends on physical and chemical properties, but also on the degree of polymeriza- tion (DP) of the polymeric material. In the present study, to understand the polarizing mechanism, two different molec- ular weights of polyvinyl alcohol (PVA) films were used for impedance analysis. Dielectric polarization of PVA film measured at normal temperature and pressure (NTP) con- dition by using LCR-4282A Impedance analyzer, within the frequency range 20 Hz to 1 MHz. The importance of inves- tigation is to know the simultaneous application of DC bias potential from 0 to 40 V with AC signal for measurement of over all electrical parameters. The result shows higher mag- nitude of dielectric constant for low-molecular weight (LMW) of PVA film in comparison to higher molecular weight (HMW), which is based on Maxwell-Wagner (M–W) theory. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1014 –1016, 2006 Key words: impedance analysis; DC bias potential INTRODUCTION The basic properties of PVA depend on its degree of polymerization and hydrolysis. Most common com- mercial grades are classified by the percentage of hy- drolysis and degree of polymerization. With expan- sions of the commercial applications, many grades of PVA have been made available: (a) a fully hydrolyzed group with degree of hydrolysis above 98% and (b) a partly hydrolyzed group with 87– 89% hydrolysis. Higher the degree of hydrolysis, higher is the molec- ular weight and vice versa. 1 Most of the workers re- ported the dielectric properties and relaxation mech- anism of polymer PVA either in the pure or composite form. 2–6 By knowing the various grades of polymer PVA, and the degree of hydrolysis that related to the molecular weight (MW), it was thought interested to study the dielectric properties of HMW and LMW of PVA film as function of frequency for various DC bias potential from 0 to 40 V, at NTP condition. This inves- tigation is rather new approach to study the dielectric polarization with help of clipped signal condition. EXPERIMENTAL Polymer PVA in the granular form of two different hydrolyzed grades 125,000 g/mol and 1700 –1800 g/mol were supplied by S.D. Fine Chem., Mumbai, and is used for synthesis of PVA film by solution- casting method. LCR-4282A impedance analyzer The dielectric constant and loss were measured by using the Impedance analyzer make Aglient 4282A precision LCR meter. Guard electrode contact method was adopted with sample size 40 mm diameter PVA film, silver pasted from both sides. The relative dielec- tric constant confirmed by measuring the out plane capacitor (C p ) with the formula relative dielectric con- stant 7 () = C p  9.96  10. 9 All the measurements were carried out at NTP condition within the fre- quency range 20 Hz to1 MHz for various DC bias potential from 0 to 40 V. The specialty of this Imped- ance analyzer is the inbuilt DC bias potential variation facilities, which enables to apply simultaneously DC potential along with AC signal for measuring over all the electrical parameters. The fixture assembly at- tached with this instrument designed to take observa- tions at NTP condition only. RESULTS AND DISCUSSION Role of DC bias potential The applications of DC bias potential (influence of direct field) from 0 to 40 V simultaneously along with AC signal clip the peaks of an AC. 8–9 The clipped Correspondence to: G. Joshi (gm_joshi@yahoomail.com). Journal of Applied Polymer Science, Vol. 102, 1014 –1016 (2006) © 2006 Wiley Periodicals, Inc.