Effects of Syndiotacticity on the Dynamic and Static Phase Separation Properties of Poly(N-isopropylacrylamide) in Aqueous Solution

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• 作者：Takanori Tada ; Tomohiro Hirano ; Koichi Ute ; Yukiteru Katsumoto ; Taka-Aki Asoh ; Tatsuya Shoji ; Noboru Kitamura ; Yasuyuki Tsuboi
• 刊名：Journal of Physical Chemistry B
• 出版年：2016
• 出版时间：August 11, 2016
• 年：2016
• 卷：120
• 期：31
• 页码：7724-7730
• 全文大小：396K
• 年卷期：0
• ISSN：1520-5207

文摘

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 (C_cp) in the concentration dependence of the phase separation rate: the phase separation accelerated dramatically when the solution concentration was higher than 2.0 wt % (= C_cp). 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.