Molecular Flow and Lanthanum -Catalyzed Bond Interchange in Sodium Phosphate Polymers |
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| Authors: | Adi Eisenberg Shogo Saito |
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| Affiliation: | 1. Department of Chemistry , University of California , Los Angeles, California;2. McGill University , Montreal, Canada;3. Japan Electrotechnical Laboratory , Tokyo, Japan |
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| Abstract: | Abstract It is observed that sodium phosphate polymers, in which some of the Na+ ions have been replaced by La3+ ions, are subject to both simple molecular flow and to bond interchange in the glass transition region. These two relaxation mechanisms are separated, and their relative contributions to the shear viscosity are calculated. It is shown that the bond-interchange mechanism is subject to an activation energy of ca. 50 kcal, while that of the molecular flow is of the order of 200 kcal at Tg + 30°C;the latter is of the WLF form. It is further shown that the La3+ ions act as cross-links, at least at low concentrations, and that bond interchange occurs at the site of the La3+ ions rather than at random along the polymer chain. |
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