Yang Li-Kun, Zhao Kong-Shuang, Xiao Jin-Xin
Department of Chemistry, Beijing Normal University, Beijing 100875, China.
Langmuir. 2006 Oct 10;22(21):8655-62. doi: 10.1021/la060907w.
Dielectric relaxation spectra of tetrabutylammonium perfluorooctanoate (TBPFO), an anionic fluorocarbon surfactant with two cloud points in aqueous solution, were investigated in the frequency range from 40 Hz to 110 MHz. Striking dielectric relaxations were observed when both the temperature-dependent and concentration-dependent phase transitions in TBPFO aqueous solution occurred. The changes in dielectric relaxation and the distribution of dielectric parameters were consistent with the phase boundaries of the phase diagram. In the first homogeneous phase region, two relaxations of rodlike micelles appeared at about 100 kHz and 5 MHz, which originated from the diffusion of the free counterions in the directions of the long axis and the short axis of rodlike micelles, respectively. With increasing temperature, two relaxations gradually turned to one as a result of the formation of connected or entanglement points between the wormlike micelles. The lengths of the long half-axis and the short half-axis of the rodlike micelles, as well as the average distance of the connected or entanglement points of the wormlike micelles, were evaluated by the obtained relaxation times.
全氟辛酸四丁基铵（TBPFO）是一种在水溶液中有两个浊点的阴离子氟碳表面活性剂，研究了其在40Hz至110MHz频率范围内的介电弛豫谱。当TBPFO水溶液中发生温度依赖性和浓度依赖性相变时，观察到显著的介电弛豫。介电弛豫的变化和介电参数的分布与相图的相边界一致。在第一个均相区域，棒状胶束在约100kHz和5MHz处出现两个弛豫，分别源于自由抗衡离子在棒状胶束长轴和短轴方向上的扩散。随着温度升高，由于蠕虫状胶束之间形成连接点或缠结点，两个弛豫逐渐变为一个。通过获得的弛豫时间评估了棒状胶束的长半轴和短半轴长度，以及蠕虫状胶束连接点或缠结点的平均距离。
