title: Effects of Syndiotacticity on the Dynamic and Static Phase Separation Properties of Poly(N-isopropylacrylamide) in Aqueous Solution.
abstract: The dynamic and static phase separation behavior in aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions is highly sensitive to the tacticity of PNIPAM. We investigated the phase separation dynamics of aqueous solutions of PNIPAM with different tacticities (atactic and syndiotactic-rich types) and found that the phase separation dynamics of syndiotactic-rich PNIPAM was much different from that of atactic-type PNIPAM. First, phase separation in syndiotactic-rich PNIPAM was faster. Second, there was a critical point (Ccp) in the concentration dependence of the phase separation rate: the phase separation accelerated dramatically when the solution concentration was higher than 2.0 wt % (= Ccp). Third, syndiotactic-rich PNIPAM required a higher thermal energy for phase separation compared to atactic PNIPAM. Such behavior can be explained on the basis of the high hydrophobicity of syndiotactic-rich PNIPAM in a dehydrated state and a diffusion-controlled aggregation model. The present study shows that precise control of the stereoregularity will open new channels toward the design and development of stimuli-responsive-polymer-based smart materials.
authors.affiliation: Graduate School of Chemical Sciences and Engineering, Hokkaido University , Sapporo 060-0810, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Tada
authors.affiliation: Department of Chemical Science and Technology, Institute of Technology and Science, The University of Tokushima , Minamijosanjima 2-1, Tokushima 770-8506, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hirano
authors.affiliation: Department of Chemical Science and Technology, Institute of Technology and Science, The University of Tokushima , Minamijosanjima 2-1, Tokushima 770-8506, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Ute
authors.affiliation: Department of Chemistry, Faculty of Science, Fukuoka University , Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Yukiteru
authors.initials: Y
authors.lastname: Katsumoto
authors.forename: Taka-Aki
authors.initials: TA
authors.lastname: Asoh
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Shoji
authors.affiliation: Graduate School of Chemical Sciences and Engineering, Hokkaido University , Sapporo 060-0810, Japan.|Division of Chemistry, Graduate School of Science, Hokkaido University , Sapporo 060-0810, Japan.
authors.forename: Noboru
authors.initials: N
authors.lastname: Kitamura
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Tsuboi