Jump to main content
Jump to site search


Effect of sodium thiocyanate and sodium perchlorate on poly(N-isopropylacrylamide) collapse

Author affiliations

Abstract

The T(collapse) of poly(N-isopropylacrylamide), PNIPAM, shows a nonlinear dependence on the concentration of NaSCN or NaClO4; in the case of NaClO4, for example, at very low concentrations of the salt, T(collapse) increases with the concentration, while it has an opposite trend at higher NaClO4 concentrations [J. Am. Chem. Soc., 2005, 127, 14505]. These puzzling experimental data can be rationalized by considering that low charge density and poorly hydrated ions, such as thiocyanate and perchlorate, interact preferentially with the surface of the polymer, and cause an increase of the magnitude of the energetic term that stabilizes swollen conformations at low salt concentrations. However, as both swollen and collapsed PNIPAM conformations are accessible to such ions in view of their large conformational freedom, the difference in the number of ions bound to PNIPAM surface upon collapse changes little on increasing the salt concentration. Thus, the energetic term that favors swollen conformations increases with salt concentration to a lesser extent than the solvent-excluded volume term (linked to the density increase caused by salt addition to water), that favors collapsed conformations, leading to a nonlinear trend of T(collapse).

Graphical abstract: Effect of sodium thiocyanate and sodium perchlorate on poly(N-isopropylacrylamide) collapse

Back to tab navigation

Publication details

The article was received on 20 Oct 2019, accepted on 28 Nov 2019 and first published on 29 Nov 2019


Article type: Paper
DOI: 10.1039/C9CP05706D
Phys. Chem. Chem. Phys., 2020, Advance Article

  •   Request permissions

    Effect of sodium thiocyanate and sodium perchlorate on poly(N-isopropylacrylamide) collapse

    A. Pica and G. Graziano, Phys. Chem. Chem. Phys., 2020, Advance Article , DOI: 10.1039/C9CP05706D

Search articles by author

Spotlight

Advertisements