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Title:
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Interaction of acrylic-maleic copolymers with H+, Na+, Mg2+ and Ca2+: Thermodynamic parameters and their dependence on medium
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Author:
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Bretti, Clemente; Crea, Francesco; Rey Castro, Carlos; Sammartano, Silvio
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Notes:
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Thermodynamic parameters for the interaction of two acrylic-maleic copolymers (MW = 3 and 70 kDa) with H+,
Na+, Mg2+ and Ca2+ were obtained from potentiometric and calorimetric measurements. Apparent protonation constants
were expressed as a function of a (dissociation degree) using the three parameter model proposed by Ho¨gfeldt
and the formation constants of Na+, Mg2+ and Ca2+ complexes were calculated from the differences in protonation
constants in the different ionic media. The salt effects on protonation were interpreted in terms of both activity coeffi-
cient variations and cation complex formation. Enthalpy changes for protonation, obtained by direct calorimetry
(always quite low, the stabilization being mainly of entropic nature), were also expressed as a function of a and I using
empirical equations. The formation constants obtained for alkali and alkaline earth metal complexes are quite low for
Na+ species (depending on a and on ionic strength, we always found K < 10 L mol 1
), and fairly high for Mg2+ and
Ca2+ species, ML and ML2
We thank Università of Messina (PRA) for financial support and Ministerio de Educación, Cultura y Deporte (Spain) for the FPU fellowship of C.R.C. |
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Subject(s):
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-Poly(acrylic-co-maleic) acids
-Potentiometry
-Calorimetry
-Medium effect |
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Rights:
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(c) Elsevier B.V., 2005
info:eu-repo/semantics/restrictedAccess |
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Document type:
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article
publishedVersion |
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Published by:
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Elsevier
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