1994 Fiscal Year Final Research Report Summary
Evaluation of the Electrostatic Effect on Ionic Reactions in Charged Polyion Systems
| Project/Area Number |
05804036
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
機能・物性・材料
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
MIYAJIMA Tohru Kyushu University, Faculty of Science, Department of Chemistry, Associate Professor, 理学部, 助教授 (40128103)
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| Co-Investigator(Kenkyū-buntansha) |
TOKO Kiyoshi Kyushu University, Faculty of Engineering, Department of Electronics, Associate, 工学部, 助教授 (50136529)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Polyelectrolytes / Ion-Exchange / Complexation equilibria / Carboxymethyldextran / Gel |
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| Research Abstract |
An electrostatic effect attributable to counterions being concentrated around the polymer skeleton makes the binding equilibria of polyion-counterions complicated. The objective of the present research project is to examine the applicability of a Gibbs-Donnan concept to evaluate the electrostatic effect in the binding equilibria of linear and cross-linked linear polyions (polyion gels). Dextran sulfate (DxS) and carboxymethyldextran (CmDx) have been used as examples of linear polyions, and sulfopropyl dextran gel and carboxymethyldextran gel have been usesd as examples of cross-linked linear polyion gels. Introduction of a volume term for the counterion concentrating region permits definition of the averaged concentrations of the ionic species in the vicinity of the polyion skeleton. Results of the counterion binding equilibrium analysis of DxS and CmDx revealed that both the Donnan potential term and the volume term for the counterion concentrating region can be expressed simply as a function of the linear charge separation of the polyion and the added salt concentration. The ionic atmosphere in the polyion domain is considered to correspond to a homogeneous concentrated electrolyte solution composed of fixed ions, counterions, and co-ions. By defining the standard state of each phase to be the same, valid insights with respect to the measured properties of the various species in the polyion domain are facilitated. Agreement of the values of the intrinsic binding constants of the monodentate complexes of CmDx and its gel analogs determined with this approach, with those of the corresponding metal complexes of their monomer analogs demonstrate the value of this approach. It has been proved by the present systematic work that the Gibbs-Donnan concept can be applied to the thermodynamic expression of the counterion binding equilibria of any polyions, irrespective of their shapes, appearances, and the nature of the fixed ions.
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