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Polymers 2017, 9(2), 66; doi:10.3390/polym9020066

Characterization of Responsive Hydrogel Nanoparticles upon Polyelectrolyte Complexation

1
Yonsei-IBS Institute, Yonsei University, Seoul 03722, Korea
2
STEM Research Institute, Fairfax, VA 22031, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Francoise Winnik
Received: 10 January 2017 / Revised: 13 February 2017 / Accepted: 13 February 2017 / Published: 16 February 2017
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Abstract

Characterization of responsive hydrogels and their interaction with other molecules have significantly expanded our understanding of the functional materials. We here report on the response of poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-co-AAc) nanogels to the addition of the poly(allylamine hydrochloride) (PAH) in aqueous dispersions. We find that the hydrodynamic radius and stability of nanogels are dependent on the PAH/nanogel stoichiometry. If the nanogel solution is titrated with very small aliquots of PAH, the nanogels decrease in radius until the equivalence point, followed by aggregation at suprastoichiometric PAH additions. Conversely, when titrated with large aliquots, the nanogel charge switches rapidly from anionic to cationic, and no aggregation is observed. This behavior correlates well with electrophoretic mobility measurements, which shows the nanogel charge transitioning from negative to positive upon PAH addition. The volume phase transition temperature (VPTT) of the nanogels is also measured to discover the effect of polyelectrolyte complexation on the deswelling thermodynamics. These data show that charge neutralization upon PAH addition decreases the VPTT of the nanogel at pH 6.5. However, if an excess amount of PAH is added to the nanogel solution, the VPTT shifts back to higher temperatures due to the formation of a net positive charge in the nanogel network. View Full-Text
Keywords: hydrogel; nanogel; polyelectrolyte; aggregation; deswelling; swelling hydrogel; nanogel; polyelectrolyte; aggregation; deswelling; swelling
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Lee, S.-K.; Hwang, G.; Woo, J.; Park, J.; Kim, J. Characterization of Responsive Hydrogel Nanoparticles upon Polyelectrolyte Complexation. Polymers 2017, 9, 66.

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