title: Phase behavior of aqueous solutions of copolymers of N,N'-diisopropylfumaramide and N-isopropylacrylamide: effect of the density of side chains.
abstract: This letter describes the phase behavior of aqueous solutions of an N-isopropylacrylamide (NIPAM) homopolymer and copolymers of N,N'-diisopropylfumaramide (DIPFAM) and NIPAM as studied by transmittance measurements, infrared spectroscopy, and differential scanning calorimetry to reveal the effect of the density of N-isopropylamide side chain upon the phase behavior. The clouding-point and clearing-point temperatures decreased with increasing the mole fraction of DIPFAM (x(D)). It was noteworthy that only an extra side chain per ca. 7 NIPAM units had a remarkable effect on the phase behavior; the interactions between side chains were stronger, the intrapolymer contraction was less favorable, and the cooperativity of phase transition was lower at x(D) = 0.15 presumably because of the steric hindrance of dense side chains.
authors.affiliation: Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan. akihito@chem.sci.osaka-u.ac.jp
authors.forename: Akihito
authors.initials: A
authors.lastname: Hashidzume
authors.forename: Akiko
authors.initials: A
authors.lastname: Matsumoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mori
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shikata
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sato