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From polyelectrolyte to polyampholyte microgels: comparison of swelling properties

From polyelectrolyte to polyampholyte microgels: comparison of swelling properties We report the results of comparative studies of the swelling behavior of polyelectrolyte (PE) and polyampholyte (PA) microgels in response to pH, ionic strength, temperature, and solvent composition. Polyelectrolyte microgels used were cross-linked binary copolymers of poly(N-isopropylacrylamide) (polyNIPAm) and acrylic acid (AA) or vinyl imidazole (VI). The PA microgels with an excess of either cationic or anionic groups swelled at low or high pH values, respectively, analogous to PE microgels. The PA microgels with similar amounts of AA and VI groups exhibited marked swelling at both high and low pH values. All PA microgels shrank in the intermediate range of pH due to electrostatic attraction between charged AA and VI moieties. In moderately concentrated salt solutions, PA microgels underwent swelling showing antipolyelectrolyte behavior. The extent of swelling of PA microgels increased with rise in AA content. The temperature-dependent contraction of both PE and PA microgels occurred at higher temperatures when AA and VI groups were charged and hydrophilic. Ion pairing between the AA and VI groups increased the extent of the temperature-induced deswelling in PA microgels. The solvent-dependent swelling of PE and PA microgels in ethanol–water mixtures was governed by competing electrostatic and cosolvency effects. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Colloid Polymer Science Springer Journals

From polyelectrolyte to polyampholyte microgels: comparison of swelling properties

Das, Mallika; Kumacheva, Eugenia
Colloid Polymer Science , Volume 284 (10) – May 20, 2006
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References (47)

Publisher
Springer Journals
Copyright
Copyright © 2006 by Springer-Verlag
Subject
Chemistry; Polymer Sciences; Soft and Granular Matter, Complex Fluids and Microfluidics; Characterization and Evaluation of Materials; Physical Chemistry; Food Science; Nanotechnology and Microengineering
ISSN
0303-402X
eISSN
1435-1536
DOI
10.1007/s00396-006-1483-x
Publisher site
See Article on Publisher Site

Abstract

We report the results of comparative studies of the swelling behavior of polyelectrolyte (PE) and polyampholyte (PA) microgels in response to pH, ionic strength, temperature, and solvent composition. Polyelectrolyte microgels used were cross-linked binary copolymers of poly(N-isopropylacrylamide) (polyNIPAm) and acrylic acid (AA) or vinyl imidazole (VI). The PA microgels with an excess of either cationic or anionic groups swelled at low or high pH values, respectively, analogous to PE microgels. The PA microgels with similar amounts of AA and VI groups exhibited marked swelling at both high and low pH values. All PA microgels shrank in the intermediate range of pH due to electrostatic attraction between charged AA and VI moieties. In moderately concentrated salt solutions, PA microgels underwent swelling showing antipolyelectrolyte behavior. The extent of swelling of PA microgels increased with rise in AA content. The temperature-dependent contraction of both PE and PA microgels occurred at higher temperatures when AA and VI groups were charged and hydrophilic. Ion pairing between the AA and VI groups increased the extent of the temperature-induced deswelling in PA microgels. The solvent-dependent swelling of PE and PA microgels in ethanol–water mixtures was governed by competing electrostatic and cosolvency effects.

Journal

Colloid Polymer Science – Springer Journals

Published: May 20, 2006

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