Dielectric relaxation of water molecules in different lyotropic structures of nonylphenoxypoly(ethylenoxy)ethanol (Ark. 9) |
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| Authors: | S Wróbel B Gestblom E Noreland J W Doane |
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| Institution: | 1. Institute of Physics, Jagellonian University , 30-059 Kraków, Reymonta 4, Poland;2. Institute of Physics, University of Uppsala , Box 530, S-751 21, Uppsala, Sweden;3. Liquid Crystal Institute, Kent State University , Kent, Ohio, 44242, U.S.A. |
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| Abstract: | Abstract Dielectric relaxation of water molecules in the lamellar, Lα, cubic and hexagonal, Hα, lyotropic structures of nonylphenoxy-poly(ethylenoxy)ethanol (Ark. 9) has been studied by dielectric time domain spectroscopy in the frequency range between 10 MHz and 10 GHz. The values of the relaxation times, obtained at room temperature, are the following: 41 ps for the Lα phase, 29 ps for the cubic phase and 22 ps for the Hα phase. As is seen, the relaxation time of bound water is distinctly higher than that of pure water, and it depends strongly on the phase structure. The relaxation times measured for the liquid-crystalline phases as well as for pure Ark. 9 obey the Arrhenius law, and the energy barriers obtained have the following values: (20 ± 2) kJ/mol for all the liquid-crystalline phases, and (30 ± 3) kJ/mol for pure Ark. 9. The former is in good agreement with the value found for bound water in lipid systems whereas the latter is characteristic of the isotropic phase of thermotropic liquid crystals. |
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