Flipping the Pressure- and Temperature-Dependent Cloud-Point Behavior in the Cononsolvency System of Poly(N-isopropylacrylamide) in Water and Ethanol
Flipping the Pressure- and Temperature-Dependent Cloud-Point Behavior in the Cononsolvency System of Poly(N-isopropylacrylamide) in Water and Ethanol
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DOI：
10.1021/ma5001139
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发表时间：
2014-02-25
期刊：
影响因子：
5.5
通讯作者：
Vana, Philipp
中科院分区：
文献类型：
--
作者：
Ebeling, Bastian;Eggers, Steffen;Vana, Philipp
研究表明，在聚N-异丙基丙烯酰胺水溶液中加入几种有机溶剂，可提高聚合物在低温/高压区的溶解度，同时降低聚合物的溶解度，从而降低其在常压下的云温度。通过在整个溶解范围内增加添加乙醇的摩尔分数，发现相分离行为与压力和温度的影响完全相反。作为特例，在摩尔分数x=0.23时，该体系在约1000bar的恒定压力下不受温度的影响而析出。测量是在压力高达3000巴、温度低至-20摄氏度的光学高压室中进行的。结果从溶剂-溶剂和溶剂-聚合物相互作用的角度进行了讨论。
It was demonstrated for several organic cononsolvents added to aqueous solutions of poly(N-isopropylacrylamide) that they lead to an increasing solubility of the polymer in the low-temperature/high-pressure region while reducing the solubility of the polymer and therefore its cloud temperature at atmospheric pressure. A complete inversion of the phase-separation behavior regarding both the effects of pressure and temperature was found by increasing the mole fraction of added ethanol over the whole cononsolvency range. As a special case, at a mole fraction of x = 0.23 the system cleared up independent of temperature at a constant pressure of about 1000 bar. The measurements were performed in an optical high-pressure cell up to pressures of 3000 bar and down to temperatures of -20 degrees C. The results are discussed in terms of solvent-solvent and solvent-polymer interactions.