Isothermal titration calorimetric studies of the acid-base properties of poly (N-isopropylacrylamide-co-4-vinylpyridine) cationic polyelectrolyte colloidal microgels

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Seidel, J., Pinkrah, V.T., Mitchell, J.C. ORCID: https://orcid.org/0000-0003-2945-3292, Chowdhry, B.Z. and Snowden, M.J. ORCID: https://orcid.org/0000-0002-1087-2692 (2004) Isothermal titration calorimetric studies of the acid-base properties of poly (N-isopropylacrylamide-co-4-vinylpyridine) cationic polyelectrolyte colloidal microgels. Thermochimica Acta, 414 (1). pp. 47-52. ISSN 0040-6031 (doi:10.1016/j.tca.2003.11.012)

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Official URL: http://dx.doi.org/10.1016/j.tca.2003.11.012

Abstract

Isothermal titration calorimetry (ITC) and potentiometric titration were used to study the protonation properties of the 4-vinylpyridine (4-VP) moiety in cationic poly(N-isopropylacrylamide-co-4-vinylpyridine) colloidal microgels [poly(NIPAM-co-4-VP)]. Calorimetric pH titrations were performed using microgels of different 4-VP content and the influence of ionic strength and counter ions have been examined. The calorimetric titration output consists of several thermal contributions reflecting the complex nature of the interactions in the aqueous microgel dispersions. In contrast to the potentiometric results, the calorimetric titration data could not be completely described by a theoretical model solely taking into account protonation equilibria. Deviations from the proposed model correlate with swelling or shrinking of the gel particles. The calorimetric results also reveal a pronounced counter-ion effect of perchlorate compared to chloride ions. In the presence of perchlorate ions, small secondary thermal effects accompany protonation of the 4-VP moiety due, in part, to kinetically limited conformational changes in the co-polymer microgel.

Item Type:	Article
Uncontrolled Keywords:	isothermal titration calorimetry, potentiometric titration, protonation, cationic colloidal microgel, 4-Vinylpyridine, co-polymer
Subjects:	Q Science > QD Chemistry
Pre-2014 Departments:	School of Science School of Science > Medway Sciences Research Group
Related URLs:	Publisher
Last Modified:	16 Apr 2020 13:26
URI:	http://gala.gre.ac.uk/id/eprint/4197

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