Is a "Cloud-Point Curve" in Aqueous Poly(N-isopropylacrylamide) Solution Binodal?
Is a "Cloud-Point Curve" in Aqueous Poly(N-isopropylacrylamide) Solution Binodal?
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DOI：
10.1021/jp9005795
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发表时间：
2009-04-23
影响因子：
3.3
通讯作者：
Yoshizaki, Takenao
中科院分区：
文献类型：
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作者：
Kawaguchi, Tomoaki;Kobayashi, Kunihiko;Yoshizaki, Takenao
研究了活性阴离子聚合法合成的线型聚N-异丙基丙烯酰胺（PNIPA）水溶液在浊点附近的透光率。结果表明，即使在稍高于浊点的温度下，透过率也趋于0 ~ 100%的恒定值，表明在溶液中的浊点处不发生宏观相分离，因此浊点曲线不符合双峰曲线。然后进行静态和动态光散射测量的线性样品的水溶液，也是通过自由基聚合，它具有随机支化的结构，在一些温度下显着低于浊点合成的另一个。结果发现，即使在这样的温度下，在水溶液中的PNIPA样品形成聚集体，聚集体的数量，尺寸和密度分布取决于链端基的种类，也取决于一级结构。
Transmittance of light passing through an aqueous solution of a linear poly(N-isopropylacrylamide) (PNIPA) sample synthesized by living anionic polymerization was examined in detail in the vicinity of its cloud point. It is found that the transmittance approaches a constant value between 0 and 100% even at a temperature slightly higher than the cloud point, indicating that macroscopic phase separation does not take place at the cloud point in the solution and therefore the cloud-point curve dose not correspond to the binodal. Static and dynamic light scattering measurements were then carried out for aqueous solutions of the linear sample and also of another one synthesized by radical polymerization, which has random-branched structure, at some temperatures considerably lower than the cloud point. It was found that both the PNIPA samples in aqueous solutions form aggregates even at such temperatures, and the number, size, and density profile of the aggregates depend on the kind of chain end group and also on the primary structure.