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Barraza RG, Olea AF, Valdebenito CE, Dougnac V, Fuentes I. Solubilization of p-nitrophenol in aggregates formed by hydrophobically modified polyelectrolytes. J Colloid Interface Sci 2005; 275:434-8. [PMID: 15178270 DOI: 10.1016/j.jcis.2004.02.076] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2003] [Accepted: 02/25/2004] [Indexed: 10/26/2022]
Abstract
The solubilization of p-nitrophenol into the hydrophobic microdomains provided by polyelectrolytes carrying alkyl side chains of different length has been investigated in aqueous solutions of pH 5.0 and 8.0. Under these pH conditions p-nitrophenol is predominantly present in its neutral and ionic forms, respectively. Potassium salts of poly(maleic acid-co-1-olefins), PA-nK2 with n = 12, 14, 16, 18, were synthesized, and the pseudo-phase model was used to determine the distribution coefficient KS, and the standard free energy of transfer Deltamut0 of p-nitrophenol between water and polymer aggregates. The results indicate that at both pH's the solubilization of p-nitrophenol increases with increasing size of the side alkyl chain; i.e., the values of KS follow the order PA-18K2 > PA-16K2 > PA-14K2 > PA-12K2. The free energies, Deltamut0, were plotted as a function of the number of carbon atoms in the side alkyl chain and a linear relation was found. From these plots contributions of -0.324 and -0.676 kJ mol(-1) per methylene group were determined at pH 5.0 and 8.0, respectively. The effect of aggregate size on the solubility of phenol is attributed to the hydrophobic contribution per CH2 group to the free energy of transfer. The hydrophobic nature of the CH2 group is suggested to derive largely from the enthalpic contribution.
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Affiliation(s)
- R G Barraza
- Departamento de Química, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile
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Barraza RG, Olea AF, Martinez F, Ruiz-Tagle I. Adsorption of hydrophobically modified polyelectrolytes at the -octane/water interface. J Colloid Interface Sci 2003; 261:559-64. [PMID: 16256569 DOI: 10.1016/s0021-9797(03)00118-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2002] [Accepted: 01/28/2003] [Indexed: 11/16/2022]
Abstract
The interfacial activity of polyelectrolytes carrying alkyl side chains of different length has been studied. Potassium salts of poly(maleic acid-co-1-olefins), PA-n K2 with n=12 , 14, 16, 18, were synthesized, and the interfacial tension at the aqueous solution/n -octane interface was measured as a function of the length of the alkyl side chain. The results show that the interfacial tension lowering, the limiting excess concentration Gamma (m), and the efficiency of adsorption pC (20) depend on the number of methylene groups in the alkyl side chain. According to Rosen the last two parameters define two different contributions to the standard free energy of adsorption: one arises from the distribution of the polymer between the bulk of the solution and the interface Delta G (dist )(0), and another comes from the configuration adopted at the interface Delta G (int )(0). These free energies were plotted as a function of the number of carbon atoms in the alkyl side chain and a linear relation was found for both of them. From these plots contributions of 0.83 and -0.58 per methylene group were determined for Delta G (0)(dist ) and Delta G (0)(int ), respectively. The positive value for the incremental free energy of distribution is attributed to the formation of a polymer micelle which is stabilized by longer alkyl side chains. On the other hand, the negative value for Delta G (0)(int ) indicates that at the interface the polymer adopts a configuration where the hydrocarbon tail is interacting with the octane molecules.
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Affiliation(s)
- R G Barraza
- Departamento de Química, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile
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Olea AF, Barraza RG, Fuentes I, Acevedo B, Martinez F. Solubilization of Phenols by Intramolecular Micelles Formed by Copolymers of Maleic Acid and Olefins. Macromolecules 2001. [DOI: 10.1021/ma0108362] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- A. F. Olea
- Departamento de Quimica, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 233, Santiago, Chile, and Departamento de Química, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile
| | - R. G. Barraza
- Departamento de Quimica, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 233, Santiago, Chile, and Departamento de Química, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile
| | - I. Fuentes
- Departamento de Quimica, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 233, Santiago, Chile, and Departamento de Química, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile
| | - B. Acevedo
- Departamento de Quimica, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 233, Santiago, Chile, and Departamento de Química, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile
| | - F. Martinez
- Departamento de Quimica, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 233, Santiago, Chile, and Departamento de Química, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile
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Abstract
The surface activity of five potassium salts from poly(maleic acid-co-vinyl-n-alkyl) was studied. The unusual behavior found is attributed to a polymer stabilization process by hydrophobic microdomains in the bulk. Copyright 1999 Academic Press.
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Affiliation(s)
- RG Barraza
- Facultad de Ciencias, Universidad de Chile, Santiago, Casilla 653, Chile
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