Dissociation of weak polymeric acids and bases

Wiley - Tập 13 Số 68 - Trang 69-84 - 1954
A. Katchalsky1, Nehemia Shavit2,1, H. S. Eisenberg1
1The Weizmann Institute of Science, Rehovot, Israel
2Part of a thesis submitted by N. Shavit (Sternberg) to the Hebrew University, Jerusalem, in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

Tóm tắt

AbstractThe electrolytic dissociation of several polymeric acids and bases in aqueous solutions has been investigated. The potentiometric behavior is well described by the following equations, For polyacids: and for polybases: pK0 is the intrinsic dissociation constant of the monomeric unit, α and β are the degrees of ionization of the polyacid and the polybase respectively, ψ0 is the electrostatic surface potential of the polyion. It is shown that ψ0 is equal to (1/ϵ) (δFe/δv) for polyacids and (1/ϵ) (δFe/δζ) for polybases where Fe is the electrostatic energy of the polyion and v or ζ the number of negative or positive ionized groups respectively. Equations for the calcualtion of ψ0 in the cases of randamly kinked and stretched polyelectrolytes are given and discussed. As the potential ψ0 can be obtained independently from electrophoretic measurements, the above equations correlate potentiometry and electrophoresis. The potentials of polymethacrylate ions were calculated from theory and obtained from electrophoretic and potentiometric measurements. The potentials obtained by the three methods agree within 3% thus justifying the use of the combined potentiometric and electrophoretic measurements for the evaluation of pK0. Application of this method to the potentiometric analysis of pectic acids gave good agreement with experiment and lead to pK0 = 3.40. Combined potentiometric‐electrophoretic analysis for polyaspartic acid gave pK0 = 3.53 and for polylsine pK0 = 10.44.

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Wiley

Tập 13 Số 68

69-84

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