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Title: | Broadband dielectric investigation on poly(vinyl pyrrolidone) and its water mixtures |
Authors: | Cerveny, Silvina ![]() ![]() ![]() |
Keywords: | Differential scanning calorimetry Glass transition Liquid mixtures Polymer solutions Solvation Water |
Issue Date: | 23-Jan-2008 |
Publisher: | American Institute of Physics |
Citation: | Journal of Chemical Physics 128, 044901 (2008). |
Abstract: | Broadband dielectric spectroscopy and differential scanning calorimetry measurements have been performed to study the molecular dynamics poly (vinyl pyrrolidone) and its water solutions in a wide range of concentrations (0 wt %<wc<55 wt %) and in the temperature range from 140 to 500 K. The dry material was completely characterized showing the presence of two relaxations in the supercooled state. The slow one has the characteristics of a Johari-Goldstein-type relaxation. On the other hand, the low temperature water dynamics in the mixtures evidences a prominent loss peak due to the reorientation of water molecules inside the polymer matrix for all the hydration levels. We show that the relaxation times are almost water concentration (wc) independent from wc>20 wt % suggesting that this dynamical process is dominated by water-water interactions. In addition, the temperature dependence of the water relaxation times exhibits a crossover from non-Arrhenius to Arrhenius behavior during cooling throughout the glass transition range, which has been interpreted as due to the constrains imposed by the rigid polymer matrix on the water molecules dynamics. |
Description: | 7 pages.-- PACS nr.: 61.25.he. |
Publisher version (URL): | http://dx.doi.org/10.1063/1.2822332 |
URI: | http://hdl.handle.net/10261/7428 |
DOI: | http://dx.doi.org/10.1063/1.2822332 |
ISSN: | 0021-9606 |
Appears in Collections: | (CFM) Artículos |
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