Cation Effects on the Phase Transition of N-isopropylacrylamide Hydrogels.
Cation Effects on the Phase Transition of N-isopropylacrylamide Hydrogels.
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DOI：
10.1002/macp.201400573
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发表时间：
2015-05
影响因子：
2.5
通讯作者：
K. J. Pastoor;C. Rice
中科院分区：
文献类型：
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作者：
K. J. Pastoor;C. Rice
由N-异丙基丙烯酰胺（NIPAM）形成的聚合物是高度水溶性的，并且经历温度诱导的相变至不溶状态。相行为是由亲水力和疏水力的竞争决定的。在这份报告中，额外的洞察力的影响，可溶性金属的相变过程中提供的显示，阳离子溶剂化艾滋病与稳定的疏水力。这降低了再水化的障碍，并降低了热力学熵和焓，获得与变温1H核磁共振光谱的NIPAM水凝胶在D2 O，NaCl，MgCl 2和CaCl 2。对于所研究的系列阳离子，观察到促进相变的增强效应的顺序为Ca ~（2+）<Mg ~（2+）< Na ~+。NaCl和MgCl 2对塌陷过程的热力学具有相似的影响。然而，显着差异的相变热力学观察MgCl 2和CaCl 2盐溶液之间。CaCl 2溶液对第1阶段焓和熵值的影响约为MgCl 2溶液的一半。这种差异可能与它们的Ca 2+电荷密度有关，Ca 2+的电荷密度大约是Mg 2+的一半。
Polymers formed from N-isopropylacrylamide (NIPAM) are highly water soluble and undergo a temperature-induced phase transition to an insoluble state. The phase behavior is determined by competing hydrophilic and hydrophobic forces. In this report, additional insight regarding the effect soluble metals have on the phase transition process is provided by showing that cation solvation aids with stabilization of hydrophobic forces. This reduces barriers to rehydration and decreases thermodynamic entropy and enthalpy, obtained with variable-temperature 1H nuclear magnetic resonance spectroscopy of NIPAM hydrogels in D2O, NaCl, MgCl2, and CaCl2. For the series of cations studied, it is observed that the order of increasing effect to facilitate the phase transition is Ca2+ < Mg2+ < Na+. NaCl and MgCl2 exhibited similar effects on the thermodynamics of the collapsing process. However, significant differences in the phase transition thermodynamics are observed between MgCl2 and CaCl2 salt solutions. The influence on Stage 1 enthalpy and entropy values for CaCl2 solutions is approximately half that of the MgCl2 solutions. This difference is likely related to their charge density of Ca2+, which is approximately half that of Mg2+.