title: Unusually large hysteresis of temperature-responsive poly(N-ethyl-2-propionamidoacrylamide) studied by microcalorimetry and FT-IR.
abstract: We reported here the full characterization of the hysteresis of the phase transition behavior of an aqueous solution of poly(N-ethyl-2-propionamidoacrylamide) (PNEPA), which has a unique alpha,alpha-disubstituted structure, by using microcalorimetry and FT-IR. Phase transition temperatures near the thermodynamic equilibrium were determined by extrapolating the scanning rate of the microcalorimetry to zero. The calculated hysteresis from the phase transition temperature was unusually very large (approximately 8 degrees C). FT-IR analysis indicated that the large hysteresis of PNEPA resulted from a coupling of intra-/intermonomeric unit hydrogen bonds, which is known to occur in a beta-sheet of proteins but has never been reported in temperature-responsive polymers. The effects of the molecular weight and polymer concentration on the hysteresis were studied by using fractionated PNEPAs and it was found that a low molecular weight and a low concentration enhanced the hysteresis.
authors.affiliation: Division of Life System, Institute of Technology and Science, The University of Tokushima, 2-1 minamijosanjima, Tokushima 770-8506, Japan.
authors.forename: Mohamed R
authors.initials: MR
authors.lastname: Berber
authors.forename: Hironori
authors.initials: H
authors.lastname: Mori
authors.forename: Inas H
authors.initials: IH
authors.lastname: Hafez
authors.forename: Keiji
authors.initials: K
authors.lastname: Minagawa
authors.forename: Masami
authors.initials: M
authors.lastname: Tanaka
authors.forename: Takuro
authors.initials: T
authors.lastname: Niidome
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Katayama
authors.forename: Atsushi
authors.initials: A
authors.lastname: Maruyama
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hirano
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Maeda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mori
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002151:Calorimetry; D006860:Hydrogen Bonding; D008970:Molecular Weight; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000180:Acrylic Resins; D011108:Polymers; C553819:poly(N-ethyl-2-propionamidoacrylamide)