DISSOCIATION BEHAVIOR OF POLY(FUMARIC ACID) AND POLY(MALEIC ACID) .1. POTENTIOMETRIC TITRATION AND INTRINSIC-VISCOSITY
DISSOCIATION BEHAVIOR OF POLY(FUMARIC ACID) AND POLY(MALEIC ACID) .1. POTENTIOMETRIC TITRATION AND INTRINSIC-VISCOSITY
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DOI：
10.1021/ma00173a028
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发表时间：
1987-07-01
期刊：
影响因子：
5.5
通讯作者：
MINAKATA, A
中科院分区：
文献类型：
--
作者：
KITANO, T;KAWAGUCHI, S;MINAKATA, A
Potentiometric titration at different concentrations of added salt and intrinsic viscosity at different degrees of dissociation were measured to study the dissociation behavior of the stereoisomeric polyacids poly (fumaric acid) and poly (maleic acid), bothof which have the same molecular formulawith a carboxyl group at every carbon in the main chain. TTie titration curves show that poly (fumaric acid) exhibits apparently two-step dissociation and poly (maleic acid) exhibits it more clearly. From analysis of the titration curves it is found that the intrinsic dissociation constants are the same for both polyacidsand almost independent of the concentrationof added salt or the type of the counterion. It also reveals a remarkable difference in the dissociation behavior between the regions a< 0.5 and a> 0.5, where a is the degree of dissociation; that is, at a> 0.5 the electrostatic free energy increases more steeply with a and depends more significantly on the charge density, the configuration of the polyacid, andthe type of the counterionthan at a< 0.5. Intrinsic viscosity of each polyacid in aqueous salt solution increases with increase of a, attains a maximum near a= 0.5, and decreases gradually beyond it. Such a complicated dissociation behavior of both polyacids is discussed in terms of the electrostatic interaction between the ionized groups existing closer to each other in comparison with that of poly (acrylic acid).
