The chain conformation and relaxation dynamics of poly(acrylic acid)-graft-poly(ethylene oxide)-graft-dodecyl in water: effect of side-chains and distribution of counterions
The chain conformation and relaxation dynamics of poly(acrylic acid)-graft-poly(ethylene oxide)-graft-dodecyl in water: effect of side-chains and distribution of counterions
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聚丙烯酸-接枝-聚环氧乙烷-接枝-十二烷基在水中的链构象和弛豫动力学：侧链和抗衡离子分布的影响
DOI：
10.1039/c4cp04530k
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发表时间：
2015
影响因子：
3.3
通讯作者：
Zhao Kongshuang
中科院分区：
文献类型：
--
作者：
Li Jingliang;Zhao Kongshuang
我们研究了两亲性共聚物聚（丙烯酸）-接枝-聚（环氧乙烷）-接枝-十二烷基（PAA-g-PEO-g-十二烷基）水溶液在不同浓度和温度下在 40 Hz 至 110 MHz 频率范围内的介电行为。消除低频电极极化后，在约1.2 MHz、150 kHz和30 kHz处观察到三个介电弛豫过程，其机制分别被证明源于自由反离子的波动、凝聚反离子的波动和分子内聚集体的旋转。这三种弛豫的介电增量 Δε 和弛豫时间 τ 的浓度依赖性在 0.15 mg ml−1 处呈现突然变化，表明 PAA-g-PEO-g-十二烷基分子经历了从分子内聚集体到分子间聚集体的构象转变。此外，Δε 和 τ 在约 317 K 时都显示出明显的转变，表明聚集体发生了部分塌陷。根据伊藤反离子波动理论估算PAA-g-PEO-g-十二烷基链的相关长度和轮廓长度。研究发现疏水/亲水侧链影响PAA的微观构象，且氢键相互作用极大地影响构象。此外，还计算了这三种弛豫的活化能，研究了离子传导过程，并利用结果讨论了反离子分布和离子传导。
We present a study on the dielectric behavior of an aqueous solution of an amphiphilic copolymer, poly(acrylic acid)-graft-poly(ethylene oxide)-graft-dodecyl (PAA-g-PEO-g-dodecyl), in the frequency range of 40 Hz to 110 MHz at varying concentrations and temperatures. After eliminating the electrode polarization at low-frequency, three dielectric relaxation processes were observed at about 1.2 MHz, 150 kHz and 30 kHz, whose mechanisms were proved to originate from the fluctuations of free counterions, the fluctuation of condensed counterions, and the rotation of intramolecular aggregates, respectively. The concentration dependence of the dielectric increment Δε and relaxation time τ for these three relaxations presents an abrupt change at 0.15 mg ml−1, indicating that PAA-g-PEO-g-dodecyl molecules undergo a conformational transition from intramolecular aggregates to intermolecular aggregates. Moreover, both Δε and τ show a clear transition at about 317 K, suggesting a partial collapse of the aggregates. The correlation length and the contour length of the PAA-g-PEO-g-dodecyl chain were estimated according to Ito's theory of counterion fluctuation. It was found that the hydrophobic/hydrophilic side-chains affected the microscopic conformation of PAA, and the hydrogen-bond interactions greatly influenced the conformation. Additionally, the activation energy of these three relaxations was calculated and the process of ionic conduction was studied and the results were used to discuss counterion distribution and ion conduction.