title: Isobars, the coexistence curve, and the critical exponent β of N-isopropylacrylamide gels obtained using a simple experimental method.
abstract: We have obtained "iso-osmobars," which refer to lines with constant osmotic pressures, and coexistence curve of the volume phase transition of N-isopropylacrylamide gel using a very simple method: hanging gels above NaCl solution having a given concentration in a sealed container that was placed in a temperature controlled bath. Since the chemical potential of the water molecules in the gel is equal to that of the water molecules in the NaCl solution, the osmotic pressure of the gel became the same value with that of the NaCl solution. Thus, air that separated the gel and the NaCl solution played a role of infinitely flexible semipermeable membrane. We have succeeded to obtain the coexistence curve and related critical exponent β from the series of the iso-osmobars of the gel. The value of β we obtained was 0.38(1.5).
authors.affiliation: Department of Physics and Mathematics, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258, Japan.
authors.forename: Kohei D
authors.initials: KD
authors.lastname: Arai
authors.forename: Azusa
authors.initials: A
authors.lastname: Saito
authors.forename: Kazuki
authors.initials: K
authors.lastname: Ito
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Uematsu
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ueno
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Fujii
authors.forename: Izumi
authors.initials: I
authors.lastname: Nishio
mesh_terms: D000178:Acrylamides / Q000737:chemistry*; D000465:Algorithms; D003198:Computer Simulation; D005782:Gels / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D011312:Pressure
chemical_list: D000178:Acrylamides; D005782:Gels