Dissolution behavior in water of a model hydrophobic alkali-swellable emulsion (HASE) polymer with C&lt;sub&gt;20&lt;/sub&gt;H&lt;sub&gt;41&lt;/sub&gt; groups

Horiuchi, Kazunaga; Rharbi, Yahya; Yekta, Ahmad; Winnik, Mitchell A.; Jenkins, R. D.; Bassett, David R.

doi:10.1139/cjc-76-11-1779

Cited by 5 publications

(6 citation statements)

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“…Two distinct equivalence points (indicated by the arrows) can be detected from the pH curves. The first equivalence point observed at α ∼ 0.1, characterizing the strong acid−base reaction, caused by the neutralization of a small amount of sulfate (∼SO 3 H) groups introduced from the initiator during the polymer synthesis. , The second equivalence point at α = 1 characterizes the complete neutralization of carboxylic groups on the polymer chains. As shown in Figure , the pH decreases with the increase of NaCl concentrations before the complete neutralization point.…”

Section: Resultsmentioning

confidence: 99%

“…One of the distinguishing features of these polymer structures is that the hydrophobic substituents are separated from the polymer backbone by a polyethylene-oxide (PEO) spacer chain. An increase in the pH causes the ionization of acid groups, leading to the solublization of latex particles, which give rise to interesting changes in the polymer conformation. − The dispersions at low pH possess a water-like viscosity. Raising the pH of a moderately concentrated polymer solution to higher than 7, produces a large increase in the solution viscosity. − …”

Section: Introductionmentioning

confidence: 99%

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Dissolution Behavior of HASE Polymers in the Presence of Salt: Potentiometric Titration, Isothermal Titration Calorimetry, and Light Scattering Studies

2002

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Potentiometric titration, static and dynamic light scattering, and isothermal titration calorimetry were used to study the salt effects on the dissolution behavior of Hydrophobically Modified Alkali-Soluble Emulsion (HASE) polymer emulsions in aqueous medium.The negative logarithm dissociation constant (pK a) curves reveal that HASE polymer exhibits a conformational transition from a compact hard sphere to a random coil during the process of neutralization. Addition of a neutral salt reduces the energy necessary to extract protons from carboxylic acid groups, which favors the neutralization process. The latex particles expand with extent of neutralization (α) in the early stage of titration, thereafter the swollen particles dissociate into smaller clusters. The addition of salt screens the electrostatic repulsion between the polymer chains, and consequently reduces the hydrodynamic radius (R h) of the polymer clusters. The results also show that the polymer chains tend to form intramolecular association rather than intermolecular association in the presence of salt, which promotes the dissociation of polymer particles. The thermodynamic quantification of the dissolution behavior of model HASE polymer was achieved using the isothermal titration calorimetric technique. The results reveal that neutralization is an exothermic process dominated by enthalpy. The comparison of the titration data in different salt conditions show that the ΔG for the neutralization process is more negative at high salt content, suggesting that the dissolution is enhanced by the presence of a neutral salt.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dissolution Behavior of HASE Polymers in the Presence of Salt: Potentiometric Titration, Isothermal Titration Calorimetry, and Light Scattering Studies

2002

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“…For telechelic HEUR system, the hydrophobes are located at both ends of the water-soluble backbones. In the past few years, several studies on the rheological behavior of HASE polymer solutions at high polymer concentrations had been reported. − To gain a better understanding on the supramolecular assembly of the polymer chains and their microstructure, laser light scattering studies on dilute HASE solutions were performed. , It was found that salt concentrations and pHs significantly alter the microstructure and the solution properties. Because the backbones of HASE contain MAA, increasing pH will enhance the neutralization of MAA groups, which causes the apparent size and configuration of the aggregates to increase due to electrostatic repulsive forces.…”

Section: Introductionmentioning

confidence: 99%

Light Scattering of Dilute Hydrophobically Modified Alkali-Soluble Emulsion Solutions: Effects of Hydrophobicity and Spacer Length of Macromonomer

et al. 2000

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A novel comb water-soluble associative polymer (hydrophobically modified alkali-soluble emulsion (HASE)), comprising of a random copolymer of methacrylic acid (MAA), ethyl acrylate (EA), and 1 mol % of hydrophobically modified macromonomers, was studied using laser light scattering and rheological techniques. The hydrophobic substituents are separated from the backbone by a poly(ethylene glycol) (PEG or PEO) spacer chain. The hydrophobicity of the hydrophobic substituents and the length of PEO spacers control the microstructure of the aggregates or clusters. In dilute solution regime, the relaxation times of both unimers and aggregates are almost independent of hydrophobic groups and PEO spacer length. The aggregates are formed via the closed-association mechanism, and the balance of electrostatic and hydrophobic interactions controls their microstructures. However, by varying the hydrophobicity and the length of the PEO spacer chains, the internal conformation of the aggregates changes. Results from static and dynamic light scattering are consistent with the trends observed from rheological measurements.

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“…Many techniques, such as fluorescence spectroscopy, pulse gradient NMR, dynamic light scattering, and rheology, can be used to investigate the behavior of the HASE polymer in aqueous solution. Several publications on the rheological properties and the fluorescence spectroscopy of this thickener have been reported. − …”

Section: Introductionmentioning

confidence: 99%

Microstructure of Dilute Hydrophobically Modified Alkali Soluble Emulsion in Aqueous Salt Solution

1999

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The microstructure of a model HASE associative polymer in aqueous salt solution is complex and has not been defined until now. On the basis of the results from static and dynamic light scattering studies, a physical model describing the microstructure of a model HASE polymer in aqueous salt solution is proposed. The model HASE polymer contains a copolymer backbone of equal moles of methacrylic acid (MAA) and ethyl acrylate (EA) with 1 mol % of C16H33 hydrophobic modified macromonomer distributed randomly along the backbone. In very dilute aqueous solutions (0.005-0.1 wt %), two decay modes are observed in the relaxation time distribution function. The fast and the slow modes correspond to the translational diffusion of the unimers and the polymer aggregates (consisting of about five polymer chains), respectively. The polymer aggregate is formed by association of the hydrophobic macromonomer via a closed association mechanism. When the polymer concentration increases, the polymer aggregates grow in size. The fractal dimension, df, decreases with increasing polymer concentrations, indicating that the aggregates are becoming less compact. At the same time, when the polymer concentration exceeds 0.1 wt %, the unimers are transformed to oligomers consisting of two or more polymer chains.

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Dissolution behavior in water of a model hydrophobic alkali-swellable emulsion (HASE) polymer with C<sub>20</sub>H<sub>41</sub> groups

Cited by 5 publications

References 0 publications

Dissolution Behavior of HASE Polymers in the Presence of Salt: Potentiometric Titration, Isothermal Titration Calorimetry, and Light Scattering Studies

Dissolution Behavior of HASE Polymers in the Presence of Salt: Potentiometric Titration, Isothermal Titration Calorimetry, and Light Scattering Studies

Light Scattering of Dilute Hydrophobically Modified Alkali-Soluble Emulsion Solutions: Effects of Hydrophobicity and Spacer Length of Macromonomer

Microstructure of Dilute Hydrophobically Modified Alkali Soluble Emulsion in Aqueous Salt Solution

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