Low frequency dielectric investigations into the relaxation behavior of frozen polyvinylpyrrolidone-water systems

Barker, S. A., He, R. and Craig, D. Q. M. (2001) Low frequency dielectric investigations into the relaxation behavior of frozen polyvinylpyrrolidone-water systems. Journal of Pharmaceutical Sciences, 90 (2). pp. 157-164. ISSN 0022-3549

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The low frequency dielectric response of aqueous solutions containing 0, 1, 5, and 10% w/v polyvinylpyrrolidone (PVP) was studied to characterize the low temperature relaxation behavior of these systems. Complementary modulated temperature differential scanning calorimetry (MTDSC) studies allowed measurement of the glass transition temperature for these materials, corresponding to the behavior of the nonfrozen phase. Dielectric investigations in the frequency range of 10(6) to 10(-2) Hz were performed on the systems in the liquid state, with a Maxwell-Wagner response noted for both the PVP solutions and water. The solid-phase responses were studied over a range of temperatures down to -70 degreesC, with a relaxation peak observed for the PVP systems in the kilohertz region. The spectra were modeled using the Havriliak-Negami equation and the corresponding relaxation times were calculated, with a satisfactory fit to the Arrhenius equation noted. The calculated activation energies were similar to literature values for the dielectric relaxation of water. It is suggested that the dielectric response is primarily a reflection of the relaxation behavior of the water molecules in the nonfrozen fraction, thereby indicating that the dielectric technique may yield insights into specific components of frozen aqueous systems. (C) 2001 Wiley-Liss, Inc.

Item Type: Article
Uncontrolled Keywords: molecular mobility,poly(vinylpyrrolidone),state,polyvinylpyrrolidone (pvp),sucrose,relaxation,polymer-solution,differential scanning calorimetry,formulations,glass,differential scanning calorimetry (mtdsc),dielectric,amorphous pharmaceutical solids,amorphous,glass-transition temperatures,freeze drying,modulated temperature
Faculty \ School: Faculty of Science > School of Pharmacy
Depositing User: Rachel Smith
Date Deposited: 11 May 2011 11:22
Last Modified: 24 Oct 2022 03:33
URI: https://ueaeprints.uea.ac.uk/id/eprint/30226

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