Indian J. Phys. 84 (4), 419-429 (2010) © 2010 IACS Dielectric relaxation and hydrogen bond interaction study of diol-water mixtures S D Chavan 1 , B D Watode 1 , P G Hudge 1 , D B Suryawanshi 1 , C G Akode 1 , A C Kumbharkhane 1* and S C Mehrotra 2 1 School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded-431 606, Maharashtra, India 2 Department of Computer Science & Information Technology, Dr. B A Marathwada University, Aurangabad-431 004, Maharashtra, India E-mail: akumbharkhane@yahoo.co.in Received 6 July 2009, accepted 12 January 2010 Abstract : Complex dielectric permittivity measurements in the frequency range 10MHz-20GHz have been carried out in diol-water mixtures over the entire concentration range using a time domain reflectometry (TDR) method at 25 0 C. A hydrogen bonded theory is applied to compute the dielectric constant for the mixtures. It adequately reproduces the experimental values of static dielectric constants for the diol-water mixtures. The dielectric parameters confirm that the intermolecular homogeneous and heterogeneous hydrogen bonding vary significantly with the increase in concentration of the constituents of the diol-water mixtures. Keywords: Dielectric permittivity, relaxation time, time domain reflectometry, molecular interactions. PACS Nos. : 77.22.Ch, 61.25.Gy, 61.25.-f, 33.15.Fm 1. Introduction Diol (Ethylene glycol and Diethylene glycol) are organic liquids and have two -OH groups at the ends of their molecular structures. Dielectric relaxation studies on diols have revealed that the microwave frequency region dielectric dispersion is attributed to the reorientation of the molecules as whole and also the end –OH groups [1-3]. Diol are soluble in water in a wide concentration range [1]. Due to the presence of ends -OH groups, the molecules of these liquids can enter into intra and intermolecular hydrogen bonding giving rise to several conformations in water mixture [2-3]. There are two kinds of water structures *Corresponding Author