STUDY OF THE REORIENTATIONAL MOTION OF RODLIKE MICELLES BY ULTRASONICALLY INDUCED BIREFRINGENCE

本工作的目的是利用超声诱导双折射法直接测量棒状胶束的取向弛豫时间，获得棒状胶束稳定性的新信息。改进了光探测器和光学系统，以测量超声诱导双折射的频率依赖性（超声诱导双折射光谱）。为了研究棒状胶体粒子的超声诱导双折射现象，测量了赤铁矿溶胶和聚四氟乙烯（PTFE）胶乳的超声诱导双折射频率特性。在5 ~ 225 MHz的宽频率范围内观察到双折射现象。对于棒状胶体颗粒，需要将Oka理论与粘性流体中的转动力矩相结合，建立一种新的超声双折射理论。合成了十六烷基二甲基甲酰胺氧化物（C16 DMAO），并测量了20和50 mM C16 DMAO水溶液的超声双折射，双折射强度在10 <-10>~ 10 °<-9>之间，并随着各向同性-均相转变点的接近而增加。双折射率与超声强度的平方根成正比，而赤铁矿溶胶和聚四氟乙烯乳液的双折射率与超声强度成正比。在本实验条件下，没有观察到棒状胶束的形状变化。从瞬态双折射的轨迹中观察到50 mM溶液的取向弛豫运动有三个不同的过程，取向弛豫时间在0.03 ~ 0.04秒之间。这一过程可归结为棒状胶束复杂的缠结运动。在低浓度范围内，观察到单一弛豫，20 mM溶液在35和50 ℃下的取向弛豫时间分别为0.31和0.24 sec。

The purpose of this work is to directly measure the orientational relaxation times of rodlike micelles and to get new information about the stability of rodlike micelles by ultrasonically induced birefringence method. The light detector and optical system were improved to measure the frequency dependence of ultrasonically induced birefringence (ultrasonically induced birefringence spectroscopy). In order to clarify ultrasonically induced birefringence of rodlike colloidal particle, the frequency dependence of ultrasonically induced birefringence was measured for hematite sol and poly (tetrafluoroehylene) (PTFE) latex. The birefringence was observed in the wide frequencyrange from 5 to 225 MHz. A new theory of ultrasonically induced birefringence should be required for the case of rodlike colloidal particle combining the Oka theory with the turning torque in viscous fluids. The hexadecyldimethylame oxides (C16DMAO) were synthesized and ultrasonically induced birefringence was measured for aqueous C16DMAO solutions of 20 and 50 mM.The intensity of the birefringence was in the range 10^<-10>-10^<-9> and increased with approaching to isotropic-nematic phase transition point. The birefringence was proportional to the square root of ultrasonic intensity, while the those of hematite soland PTFE latex were proportional to the ultrasonic intensity. The change of shape of rod like micelles was not observed within our experimental condition. The three different processes of orientational relaxation motions of solutions of 50mM were observed from the trace of the transient birefringence and the orientational relaxation times lied from 0.03 to 0.04 sec. The processes are as cribed to the motion of the complicated entanglement of the rod like micelles. In the range of the low concentration of micelle, the single relaxation was observed and the orientational relaxation times for 20 mM solution at 35 and 50 ﾟC were 0.31 and 0.24 sec, respectively.