Dynamics in N-isopropylacrylamide-acrylic acid copolymer aqueous solution from mechanical spectroscopy.
Dynamics in N-isopropylacrylamide-acrylic acid copolymer aqueous solution from mechanical spectroscopy.
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DOI：
10.1021/jp306531b
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发表时间：
2012-11
期刊：
影响因子：
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通讯作者：
Huaguang Wang;Xuebang Wu;C. S. Liu;Zhen-Gang Zhu;Zhuo Ao;Guangzhao Zhang
中科院分区：
文献类型：
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作者：
Huaguang Wang;Xuebang Wu;C. S. Liu;Zhen-Gang Zhu;Zhuo Ao;Guangzhao Zhang
获得对胶体系统的精确和可预测的结构的控制和理解丰富的动力学行为仍然是一个艰巨的挑战。在这项研究中，低频力学光谱应用于研究的N-异丙基丙烯酰胺-丙烯酸（NIPAM-AA）共聚物的水溶液的动力学与三个不同的AA含量。低AA摩尔分数（f（AA））（f（AA）= 25和50 mol %）的溶液出现一个力学损耗谷，f（AA）= 75 mol %的溶液出现一个力学损耗峰。前者是由于在低临界溶解温度以上排斥性胶束的颗粒玻璃相，而后者则与高浓度NIPAM-AA/水混合物的α弛豫行为有关。α弛豫的弛豫时间似乎遵循简单的Arrhenius温度依赖性。活化能H = 1.53 kJ/mol，H值较大可能是由于共聚物溶液中存在多个强氢键。本工作表明，通过控制胶体体系中各组分的比例，体系可以表现出明显的动力学行为，这对胶体的设计和制备很有帮助。
Gaining control over precise and predictable structures of colloidal systems and understanding the abundant dynamic behaviors remains a formidable challenge. In this study, low-frequency mechanical spectroscopy was applied to investigate the dynamics of aqueous solutions of N-isopropylacrylamide-acrylic acid (NIPAM-AA) copolymers with three different AA contents. A mechanical loss valley was found for the solution with low molar fraction of AA (f(AA)), f(AA) = 25 and 50 mol %, and a loss peak was shown for the solution with f(AA) = 75 mol %. The former is suggested to be due to the particle glass phase of repulsive micelles above the low critical solution temperature, whereas the latter is associated with the α relaxation behavior of NIPAM-AA/water mixture at high concentrations. The relaxation time of the α relaxation seems to follow a simple Arrhenius temperature dependence. The activation energy H is ∼53 kJ/mol, and the larger H value is suggested to be due to multiple strong hydrogen bonds in the copolymer solution. The present work demonstrates that by controlling the proportion of ingredients in the colloidal systems the systems can exhibit distinct dynamic behaviors, which is helpful in the design and fabrication of colloids.