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Gupta AK. Combined Salt Concentration and Degree-of-Ionization Effect on the Structure of Poly(methacrylic acid) in Aqueous Solutions as Revealed by Molecular Dynamics Simulations. Ind Eng Chem Res 2021. [DOI: 10.1021/acs.iecr.1c00492] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Abhishek Kumar Gupta
- Department of Chemical Engineering, School of Technology, Pandit Deendayal Energy University, Gandhinagar, Gujarat 382426, India
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2
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Kumar Y, Gupta AK, Natarajan U. Conformational and intermolecular structure of stereoregular isomers of poly(acrylic acid) (PAA) and Na+-poly(acrylate) polyelectrolyte (Na+-PAA) in dilute aqueous solution: a molecular dynamics simulation study. MOLECULAR SIMULATION 2020. [DOI: 10.1080/08927022.2020.1846036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Yogendra Kumar
- Macromolecular Modeling and Simulation Laboratory, Department of Chemical Engineering, Indian Institute of Technology (IIT) Madras, Chennai, India
| | - Abhishek K. Gupta
- Macromolecular Modeling and Simulation Laboratory, Department of Chemical Engineering, Indian Institute of Technology (IIT) Madras, Chennai, India
| | - Upendra Natarajan
- Macromolecular Modeling and Simulation Laboratory, Department of Chemical Engineering, Indian Institute of Technology (IIT) Madras, Chennai, India
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3
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Gupta AK, Natarajan U. Structure and dynamics of atactic Na+-poly(acrylic) acid (PAA) polyelectrolyte in aqueous solution in dilute, semi-dilute and concentrated regimes. MOLECULAR SIMULATION 2019. [DOI: 10.1080/08927022.2019.1608987] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Abhishek K. Gupta
- Department of Chemical Engineering, Macromolecular Modeling and Simulation Laboratory, Indian Institute of Technology (IIT) Madras, Chennai, India
| | - Upendra Natarajan
- Department of Chemical Engineering, Macromolecular Modeling and Simulation Laboratory, Indian Institute of Technology (IIT) Madras, Chennai, India
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Gupta AK, Natarajan U. Anionic polyelectrolyte poly(acrylic acid) (PAA) chain shrinkage in water–ethanol solution in presence of Li+ and Cs+ metal ions studied by molecular dynamics simulations. MOLECULAR SIMULATION 2017. [DOI: 10.1080/08927022.2017.1279288] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Abhishek K. Gupta
- Macromolecular Modeling and Simulation Laboratory, Department of Chemical Engineering, Indian Institute of Technology (IIT) Madras, Chennai, India
| | - Upendra Natarajan
- Macromolecular Modeling and Simulation Laboratory, Department of Chemical Engineering, Indian Institute of Technology (IIT) Madras, Chennai, India
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Kogej K. Thermodynamic Analysis of the Conformational Transition in Aqueous Solutions of Isotactic and Atactic Poly(Methacrylic Acid) and the Hydrophobic Effect. Polymers (Basel) 2016; 8:polym8050168. [PMID: 30979264 PMCID: PMC6432447 DOI: 10.3390/polym8050168] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 04/15/2016] [Accepted: 04/20/2016] [Indexed: 11/17/2022] Open
Abstract
The affinity of amphiphilic compounds for water is important in various processes, e.g., in conformational transitions of biopolymers, protein folding/unfolding, partitioning of drugs in the living systems, and many others. Herein, we study the conformational transition of two isomer forms of poly(methacrylic acid) (PMA), isotactic (iPMA) and atactic (aPMA), in water. These isomers are chemically equivalent and differ only in the arrangement of functional groups along the chain. A complete thermodynamic analysis of the transition of the PMA chains from the compact to the extended form (comprising the conformational transition) in water in the presence of three alkali chlorides is conducted by determining the free energy, enthalpy, and entropy changes of the process as a function of temperature, and therefrom also the heat capacity change. The heat capacity change of the transition is positive (+20 J/K mol) for aPMA and negative (−50 J/K mol) for iPMA. This result suggests a different affinity of PMA isomers for water. The conformational transition of iPMA is parallel to the transfer of polar solutes into water, whereas that of aPMA agrees with the transfer of nonpolar solutes into water.
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Affiliation(s)
- Ksenija Kogej
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia.
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Gupta AK, Natarajan U. Tacticity effects on conformational structure and hydration of poly-(methacrylic acid) in aqueous solutions-a molecular dynamics simulation study. MOLECULAR SIMULATION 2015. [DOI: 10.1080/08927022.2015.1086485] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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7
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Wang X, Ye X, Zhang G. Investigation of pH-induced conformational change and hydration of poly(methacrylic acid) by analytical ultracentrifugation. SOFT MATTER 2015; 11:5381-5388. [PMID: 26059391 DOI: 10.1039/c5sm00806a] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Analytical ultracentrifugation was performed on poly(methacrylic acid) (PMAA) with a series of weight average molar masses (Mw) in aqueous solutions as a function of pH. The scales of the sedimentation coefficient (s) and the diffusion coefficient (D) to Mw at infinite dilutions were obtained at different pH values, indicating that PMAA chains adopt a collapsed structure at low pH values, and stretch at pH higher than 5.2. Our results show that the sedimentation coefficient exhibits a minimum at pH ∼ 6.0, presumably due to the effect of the conformational change and the hydration state of PMAA chains. When pH increases from 6.0 to 8.5, PMAA chains with high molar mass shrink a little bit, presumably because the sodium ions act as a bridging agent between nonadjacent carboxylate groups. Furthermore, the weight average molar mass of PMAA at pH 8.5 increases by one fold than that at pH 4.0, indicating the condensation of sodium ions and the increase in the number of hydration water molecules around carboxylate groups at high pH values.
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Affiliation(s)
- Xiaoyan Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
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Chockalingam R, Natarajan U. Dynamics of conformations, hydrogen bonds and translational diffusion of poly(methacrylic acid) in aqueous solution and the concentration transition in MD simulations. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1024776] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Sitar S, Aseyev V, Kogej K. Microgel-like aggregates of isotactic and atactic poly(methacrylic acid) chains in aqueous alkali chloride solutions as evidenced by light scattering. SOFT MATTER 2014; 10:7712-7722. [PMID: 25137480 DOI: 10.1039/c4sm01448k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A comparative light-scattering study of isotactic and atactic poly(methacrylic acid), iPMA and aPMA, respectively, in aqueous solutions with added alkali chlorides, XCl (X = Li, Na, Cs), at 25 °C and XCl concentration of 0.1 mol L(-1), demonstrates that both PMA isomers are strongly associated at low degrees of neutralization, αN (= 0 for aPMA and 0.25 for iPMA), in the presence of all XCls. The shape parameter ρ and the scattering functions suggest that aggregates have the characteristics of microgel particles, with a dense core surrounded by a less dense shell. The extent of aggregation depends on the stereoregular structure of the polymer and on the type of the added cation. Li(+) and Na(+) ions support aggregation better than Cs(+) ions. Besides, iPMA chains are more strongly aggregated than aPMA chains and form particles with a denser core. A model of the aggregation process is suggested for iPMA. At high αN, a slow diffusive process (so-called extraordinary or anomalous mode in diffusion of polyelectrolytes), arising from electrostatic interactions between charged chains, is observed for both PMAs. Results suggest that under the same experimental conditions iPMA is effectively more charged than aPMA. The role of ions in the slow-mode phenomenon is less pronounced than in aggregation.
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Affiliation(s)
- Simona Sitar
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, P.O. Box 537, SI-1001, Ljubljana, Slovenia.
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Chockalingam R, Natarajan U. Self-association behaviour ofatacticpolymethacrylic acid in aqueous solution investigated by atomistic molecular dynamics simulations. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2014.947481] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Sitar S, Aseyev V, Kogej K. Differences in association behavior of isotactic and atactic poly(methacrylic acid). POLYMER 2014. [DOI: 10.1016/j.polymer.2014.01.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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12
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Kogej K, Fonseca SM, Rovisco J, Azenha ME, Ramos ML, Seixas de Melo JS, Burrows HD. Understanding the interaction between trivalent lanthanide ions and stereoregular polymethacrylates through luminescence, binding isotherms, NMR, and interaction with cetylpyridinium chloride. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:14429-14437. [PMID: 24175706 DOI: 10.1021/la4036024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Complexation of isotactic, syndiotactic, and atactic poly(methacrylic acid), PMA, with trivalent lanthanide ions has been studied in water at a degree of neutralization 0.5. Metal ion binding is shown by quenching of cerium(III) fluorescence, enhancement of Tb(III) luminescence, and lanthanide-induced line broadening in the PMA (1)H NMR spectra. Comparison with lanthanide-acetate complexation suggests carboxylate binds in a bidentate fashion, while Ce(III) luminescence quenching suggests an ≈3:1 carboxylate:metal ion stoichiometry, corresponding to charge neutralization. The presence of both free and bound Ce(III) cations in PMA solutions is confirmed from luminescence decays. Studies of Tb(3+) luminescence lifetime in H2O and D2O solutions show complexation is accompanied by loss of 5-6 water molecules, indicating that each bidentate carboxylate replaces two coordinated water molecules. The behavior depends on pH and polyelectrolyte stereoregularity, and stronger binding is observed with isotactic polyelectrolyte. Binding of cetylpyridinium chloride, CPC, in these systems is studied by luminescence, NMR, and potentiometry. NMR and Tb(3+) luminescence lifetime studies show the strongest binding with the isotactic polymer. Binding of surfactant to poly(methacrylate) in the presence of lanthanides is noncooperative, i.e., it binds to the free sites; binding isotherms in the presence of lanthanides are shifted to higher free surfactant concentrations, compared with sodium ions, have lower slopes and show a clear two-step binding mechanism. While CPC readily replaces the Na(+) ions of poly(methacrylate) and binds very strongly (low critical association concentrations), exchange is much more difficult with the strongly bound trivalent lanthanide ions. Effects of tacticity are seen, with surfactant interacting most strongly with isotactic chains in the initial stages of binding, while in the final stages of binding the interaction is strongest with atactic poly(methacrylate).
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Affiliation(s)
- Ksenija Kogej
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana , Aškerčeva 5, P.O. Box 537, SI-1000 Ljubljana, Slovenia
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Sulatha MS, Natarajan U. Molecular Dynamics Simulations of PAA–PMA Polyelectrolyte Copolymers in Dilute Aqueous Solution: Chain Conformations and Hydration Properties. Ind Eng Chem Res 2012. [DOI: 10.1021/ie301244n] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Muralidharan S. Sulatha
- Molecular Modeling and Simulation
Lab, Department of Chemical Engineering, Indian Institute of Technology − Madras, Chennai − 600036,
India
| | - Upendra Natarajan
- Molecular Modeling and Simulation
Lab, Department of Chemical Engineering, Indian Institute of Technology − Madras, Chennai − 600036,
India
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Kogej K. Association and structure formation in oppositely charged polyelectrolyte-surfactant mixtures. Adv Colloid Interface Sci 2010; 158:68-83. [PMID: 19464666 DOI: 10.1016/j.cis.2009.04.003] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 04/09/2009] [Accepted: 04/27/2009] [Indexed: 11/28/2022]
Abstract
Investigations dealing with association behaviour and structure formation in oppositely charged polyelectrolyte-surfactant mixtures in aqueous solutions are reviewed. Discussion is limited to a selection of vinyl based anionic polyelectrolytes that, when completely ionized, posses the same structural value of the linear charge density parameter. Particular emphasis is placed on the role of polymer chain properties in aggregates with surfactants. Chain characteristics are varied by changing the nature of the charged group, its ionization degree - when possible, the spatial distribution of these groups along the chain, i.e. the tacticity, and the hydrophobic character of other substituents attached to the chain. Quantitative information on the degree of binding in the form of binding isotherms is obtained using surfactant-sensitive membrane electrodes and microstructures of polyelectrolyte-surfactant complexes are determined by synchrotron small angle X-ray scattering. Considerable differences in the degree of binding (including the critical association concentration, CAC, values) and in structures are found. It is concluded that strong interactions in these systems arise from the electrostatic attraction, but this only forms the basis for initial extensive accumulation (anchoring) of surfactant ions in the vicinity of the polyion chain. When this is accomplished, additional specific interactions and effects may come into play. The most powerful of these interactions, the hydrophobic association between the chain and the micelle core, were found in polystyrenesulfonate, PSS, solutions. Other properties are less influential but still lead to CAC values that differ by more than one order of magnitude. These differences are explained by taking into account the chain conformation, flexibility, and hydrophobic character. Specific interactions between PSS and cetylpyridinium, CP, cations result in a soluble non-stoichiometric PSS-CP complex that could be characterized by measuring various solution properties as a function of polymer concentration and degree of complexation. The review is supplemented by including studies of complexation between the spherical fullerene hexamalonate anion and cationic surfactants, which demonstrate a high association tendency with characteristics similar to those found in binding of surfactants by linear polyelectrolytes.
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Affiliation(s)
- Ksenija Kogej
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Slovenia.
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Peljhan S, Žagar E, Cerkovnik J, Kogej K. Strong Intermolecular Association between Short Poly(ethacrylic acid) Chains in Aqueous Solutions. J Phys Chem B 2009; 113:2300-9. [DOI: 10.1021/jp806312u] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sebastijan Peljhan
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, P.O. Box 537, SI-1001 Ljubljana, Slovenia, and National Institute of Chemistry Slovenia, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
| | - Ema Žagar
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, P.O. Box 537, SI-1001 Ljubljana, Slovenia, and National Institute of Chemistry Slovenia, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
| | - Janez Cerkovnik
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, P.O. Box 537, SI-1001 Ljubljana, Slovenia, and National Institute of Chemistry Slovenia, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
| | - Ksenija Kogej
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, P.O. Box 537, SI-1001 Ljubljana, Slovenia, and National Institute of Chemistry Slovenia, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
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Jerman B, Breznik M, Kogej K, Paoletti S. Osmotic and Volume Properties of Stereoregular Poly(methacrylic acids) in Aqueous Solution: Role of Intermolecular Association. J Phys Chem B 2007; 111:8435-43. [PMID: 17388472 DOI: 10.1021/jp0676080] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Osmotic coefficients, phi, and apparent molar volumes, PhiV, of aqueous solutions of isotactic, syndiotactic, and atactic poly(methacrylic acid), i-PMA, s-PMA, and a-PMA, respectively, were measured at 298 K in dependence on polymer concentration and on degree of neutralization, alphaN, of carboxyl groups. The solutions of i-PMA have lower phi values than those of a-PMA and s-PMA in the whole region of alphaN. Molecular dynamics simulation studies of the isotactic and the syndiotactic PMA 101-mer have shown that lower phi is a consequence of a shorter distance between charges, which leads to a greater charge density of the isotactic polymer and thus to stronger binding of counterions. The experimental phi data were analyzed using a cylindrical cell model. Good agreement between theory and experiment was achieved when charges on the polyion were distributed periodically along the z-axis of the polyion in accordance with the simulation results. The alphaN dependence of the PhiV data pointed out that all PMA isomers bind an appreciable amount of water in the elementary dissociation process (electrostriction). For a- and s-PMA, the PhiV values decrease linearly with increasing alphaN, whereas they show a marked nonlinear dependence in the case of i-PMA for alphaN < 0.6. The latter finding was ascribed to a very high intermolecular association tendency of the isotactic polymer. This association tendency of PMA chains was confirmed by light scattering measurements. It is present in both i- and a-PMA solutions but is much more pronounced in the i-PMA case.
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Affiliation(s)
- Bostjan Jerman
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, P. O. Box 537, SI-1000 Ljubljana, Slovenia
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Delben F, Paoletti S, Porasso RD, Benegas JC. Potentiometric Titrations of Maleic Acid Copolymers in Dilute Aqueous Solution: Experimental Results and Theoretical Interpretation. MACROMOL CHEM PHYS 2006. [DOI: 10.1002/macp.200600479] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Vlachy N, Dolenc J, Jerman B, Kogej K. Influence of Stereoregularity of the Polymer Chain on Interactions with Surfactants: Binding of Cetylpyridinium Chloride by Isotactic and Atactic Poly(methacrylic acid). J Phys Chem B 2006; 110:9061-71. [PMID: 16671715 DOI: 10.1021/jp060422g] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Association of a cationic surfactant cetylpyridinium chloride, CPC, with isotactic and atactic poly(methacrylic acid), i-PMA and a-PMA, respectively, in aqueous 0.01 M NaCl solutions was studied by pH and fluorescence measurements in conjunction with potentiometric studies using a surfactant-sensitive membrane electrode. pH measurements have demonstrated that the presence of an oppositely charged surfactant increases ionization of carboxyl groups on PMA at low degrees of neutralization. The increase is more pronounced in the case of i-PMA. The isotactic form of PMA is not soluble in water at zero degrees of neutralization but can be rendered soluble by the addition of CPC at the surfactant to a polyion molar ratio of around 0.4. In the solubilized complex, the positive charge of the CPC molecule is facing the polar solvent, whereas surfactant tails are oriented toward the i-PMA compact coil. Binding isotherms and cooperativity parameters show that chain tacticity has an important influence on the interaction of cetylpyridinium cation with polymethacrylate anion. At the onset of cooperative binding, the association is stronger with i-PMA than with the atactic form, as demonstrated by lower CAC values and higher values of the cooperativity parameters. In contrast, more surfactant is bound by a-PMA in the region where polyion becomes saturated with surfactant ions. Results are interpreted by taking into account local chain conformations as obtained from quantum mechanical semiempirical molecular orbital calculations. Greater hydrophobicity and possibly higher charge density of i-PMA on one hand and more flexibility of the a-PMA chain on the other are held responsible for these observations.
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Affiliation(s)
- Nina Vlachy
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, P.O. Box 537, SI-1000 Ljubljana, Slovenia
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