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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• 作者：Bastian Ebeling ; Steffen Eggers ; Michael Hendrich ; Annika Nitschke ; Philipp Vana
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：February 25, 2014
• 年：2014
• 卷：47
• 期：4
• 页码：1462-1469
• 全文大小：404K
• 年卷期：v.47,no.4(February 25, 2014)
• ISSN：1520-5835

文摘

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 鈭?0 掳C. The results are discussed in terms of solvent鈥搒olvent and solvent鈥損olymer interactions.