Thermally sensitive reversible microgels formed by poly(N-Isopropylacrylamide) charged chains: A Hofmeister effect study

•Stable PNIPAM particles are reversible formed from single charged chains.•Hydration/dehydration of PNIPAM is extremely sensitive to test Hofmeister effects.•Particle diameter as well as the surface charge is controlled by ionic specificity.•Higher hydrated ions interact strongly to favor higher deh...

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Bibliographic Details
Published in:Journal of colloid and interface science 2014-07, Vol.426 (426), p.300-307
Main Authors: López-León, Teresa, Ortega-Vinuesa, Juan L., Bastos-González, Delfi, Elaissari, Abdelhamid
Format: Article
Language:English
Subjects:
Agglomeration
Cationic
Chains (polymeric)
Charging
Chemical Sciences
Chemistry
Colloidal gels. Colloidal sols
Colloidal state and disperse state
Colloids
Dispersions
Electrokinetic behavior
Electrokinetics
Electrolytes
Exact sciences and technology
General and physical chemistry
Hofmeister effects
Life Sciences
Material chemistry
Microgels
Pharmaceutical sciences
Polymers
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Summary:•Stable PNIPAM particles are reversible formed from single charged chains.•Hydration/dehydration of PNIPAM is extremely sensitive to test Hofmeister effects.•Particle diameter as well as the surface charge is controlled by ionic specificity.•Higher hydrated ions interact strongly to favor higher dehydration of PNIPAM.•Poorer hydrated ions accumulated on pNIPAM as this becomes more hydrophobic. In this study, we present a new method to obtain anionic and cationic stable colloidal nanogels from PNIPAM charged chains. The stability of the particles formed by inter-chain aggregation stems from the charged chemical groups attached at the sides of PNIPAM polymer chains. The particle formation is fully reversible—that is, it is possible to change from stable polymer solutions to stable colloidal dispersions and vice versa simply by varying temperature. In addition, we also demonstrate that the polymer LCST (lower critical solution temperature), the final particle size and the electrokinetic behavior of the particles formed are highly dependent on the electrolyte nature and salt concentration. These latter results are related to Hofmeister effects. The analysis of these results provides more insights about the origin of this ionic specificity, confirming that the interaction of ions with interfaces is dominated by the chaotropic/kosmotropic character of the ions and the hydrophobic/hydrophilic character of the surface in solution.
ISSN:0021-9797
1095-7103
DOI:10.1016/j.jcis.2014.04.020