A time domain spectroscopic study of polysorbates and their aqueous binary mixtures

The complex permittivity spectra of binary mixtures of polysorbates with water over entire concentration range at different temperatures (25°C, 20°C, 15°C) have been studied using time domain reflectometry (TDR) technique in the frequency range of 10 MHz–50 GHz. The complex permittivity spectra were fitted to Cole–Davidson model using non-linear least square fit method. The dielectric parameters, such as static dielectric permittivity, relaxation time and asymmetric distribution parameter have been determined for polysorbate-20 + water, polysorbate- 40 + water, polysorbate-80 + water binary mixtures. The Hydrogen bonding interactions between associating molecules have been discussed through the determination of Excess permittivity, Thermodynamic parameter & Bruggeman factor.