Dielectric Relaxation of Spherical Polyelectrolyte Brushes: Movement of Counterions and Electrical Properties of the Brush Layer
Dielectric Relaxation of Spherical Polyelectrolyte Brushes: Movement of Counterions and Electrical Properties of the Brush Layer
复制标题
球形聚电解质刷的介电弛豫：反离子的运动和刷层的电性能
DOI：
10.1021/acs.langmuir.5b01408
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发表时间：
2015
期刊：
影响因子：
3.9
通讯作者：
Zhao Kongshuang
中科院分区：
文献类型：
--
作者：
Wu Haiyan;Zhao Kongshuang
在 40 Hz 至 110 MHz 的频率范围内研究了球形聚电解质刷 (SPB) 悬浮液在不同 SPB 质量分数和溶液 pH 值下的介电行为。 SPB 由聚苯乙烯 (PS) 核接枝聚丙烯酸 (PAA) 链组成。分别在约 10 kHz 或 1-10 MHz 处发现了两个独特的弛豫，前者是由于反离子的扩散造成的，后者是由于界面极化造成的。利用两次弛豫的介电参数，我们获得了有关反离子迁移和聚电解质链构象的信息。当pH值约为8时，在刷子中抗衡离子的渗透和扩散之间的平衡的支配下，PAA链完全伸展。提出了描述高频弛豫的介电模型，并根据该模型计算了SPB的介电常数和电导率及其体积分数。 SPB 的表面电导率、Donnan 电势和刷层中的固定电荷密度均由这些参数得出。还利用Poisson-Boltzmann方程模拟了Donnan势的分布，结果与基于介电模型获得的结果一致。
Dielectric behaviors of spherical polyelectrolyte brush (SPB) suspensions under various mass fractions of SPB and the pH of solution were investigated in a frequency range of 40 Hz to 110 MHz. The SPB consists of a polystyrene (PS) core grafted with poly(acrylic acid) (PAA) chains. Two unique relaxations were found at either about 10 kHz or 1–10 MHz, respectively, with the former due to the diffusion of counterions and the latter resulting from the interfacial polarization. Using dielectric parameters of two relaxations, we obtained information about the migration of counterion and the conformation of polyelectrolyte chains. The PAA chains are fully stretched when pH is about 8 under the domination of the equilibrium between the penetration and diffusion of counterions in the brushes. A dielectric model is proposed to describe the high-frequency relaxation, and the permittivity and conductivity of SPB and its volume fraction were also calculated on the basis of the model. The surface conductivity of SPB, the Donnan potential, and the fixed charge density in the brush layer were derived from these paramaters. The distribution of the Donnan potential was also simulated by using Poisson–Boltzmann equations, and the result is in accordance with these obtained on the basis of the dielectric model.