Salt effect on volume phase transition of a gel

Annaka Masahiko, Yuko Amo, Shigeo Sasaki, Yasunori Tominaga, Keiko Motokawa, Takayuki Nakahira

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The salt effect on the phase transition of N-isopropylacrylamide (NIPA) gel was studied for alkali-metal chlorides (NaCl, KCl, and CsCl). Low-frequency Raman scattering experiment was conducted to know the dynamic state of water molecule under the presence of salt and its correlation to macroscopic phase behavior of the gel was investigated together with the thermodynamic activities of water molecule of aqueous alkali-metal chloride solutions. The series of swelling experiment reveal that the change in the gel volume phase transition strongly depends on the salt concentration and is related to the dehydration with respect to hydrophobic hydration. From the analysis of the reduced low-frequency Raman spectra in water and aqueous alkali-metal chlorides solutions by the use of the relaxation mode that takes into account the inertia and the non-white effects, the characteristic values of aqueous salt solutions (i.e., relaxation time and modulation speed) indicate that the addition of alkali-metal chloride to gel fluid affects the disruption of water molecules in the hydration shell around the NIPA gel and the formation of the hydrogen-bonded network structure of water around themselves, as a result of which the gel collapses. The chemical potential and the dynamic nature of water molecule at the transition points are well correlated: the chemical potentials at the transition points are almost constant whereas the structure of bulk water is changed by addition of alkali-metal chlorides or change in temperature. These results strongly suggest that the swelling ratio of N-isopropylacrylamide gel is a function of hydration degree, which is regulated by the chemical potential of water.

Original languageEnglish
JournalPhysical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics
Volume65
Issue number3
DOIs
Publication statusPublished - Jan 1 2002
Externally publishedYes

Fingerprint

Salt
Phase Transition
gels
salts
Water
alkali metals
Metals
chlorides
water
Hydration
Chemical Potential
Molecules
hydration
Raman Spectra
Swelling
transition points
swelling
Low Frequency
molecules
Raman spectra

All Science Journal Classification (ASJC) codes

  • Statistical and Nonlinear Physics
  • Mathematical Physics
  • Condensed Matter Physics
  • Physics and Astronomy(all)

Cite this

Salt effect on volume phase transition of a gel. / Masahiko, Annaka; Amo, Yuko; Sasaki, Shigeo; Tominaga, Yasunori; Motokawa, Keiko; Nakahira, Takayuki.

In: Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 65, No. 3, 01.01.2002.

Research output: Contribution to journalArticle

Masahiko, Annaka ; Amo, Yuko ; Sasaki, Shigeo ; Tominaga, Yasunori ; Motokawa, Keiko ; Nakahira, Takayuki. / Salt effect on volume phase transition of a gel. In: Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics. 2002 ; Vol. 65, No. 3.
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