Investigation of NiPAM interaction in aqueous solutions of salts

In this contribution we have studied the physico-chemical properties of N−isopropylacrylamide (NiPAM) in aqueous solutions of sodium and guanidinium salts [1,2]. To cover the whole diversity of the Hofmeister series three... [ view full abstract ]

In this contribution we have studied the physico-chemical properties of N−isopropylacrylamide (NiPAM) in aqueous solutions of sodium and guanidinium salts [1,2]. To cover the whole diversity of the Hofmeister series three different anions were chosen, in particular SO₄^2-, Cl^- and SCN^-. To quantify the NiPAM−salt interaction, we have determined the preferential interaction coefficient of salts over water to the NiPAM by vapor pressure osmometry (VPO) [3] and the partial molar volume of NiPAM via density measurements. Acquired data were used to calculate salting out (Setschenow) constants according to the Kirkwood-Buff theory. Moreover this gained insight was employed in the interpretation of the thermodynamic effect of salts on the collapse transition of the related thermoresponsive polymer polyNiPAM.

References:

[1]       Heyda, J.; Okur, H. I.; Hladíková, J.; Rembert, K. B.; et al. Guanidinium can both Cause and Prevent the Hydrophobic Collapse of Biomacromolecules. J. Am. Chem. Soc. 2017, 139 (2), 863–870.

[2]       Sasaki, S.; Okabe, S.; Effects of Ions on the Solubility Transition and the Phase-Separation of N-Isopropylacrylamide in Water. J. Phys. Chem. B 2011, 115, 12905−12910. 

[3]       Record, M. T., Jr.; Guinn, E.; Pegram, L.; Capp, M., Introductory Lecture: Interpreting and Predicting Hofmeister Salt Ion and Solute Effects on Biopolymer and Model Processes Using the Solute Partitioning Model. Faraday Discuss. 2013, 160, 9-44.