溴代十四烷基吡啶胶团长大的光子相关谱研究

本文用光子相关谱方法在15—85 ℃温度范围内, 研究了溴代十四烷基吡啶(TPB)胶团在高盐量介质(0.5—2.0M NaBr)中的长大规律。自光子相关实验测定了胶团的平均流体力学半径。增加盐量、降低温度和增大活性剂浓度均使胶团变大。TPB胶团长大时由球转变为棒。自实验测量结果求算了在0.5 M和1.0 M盐中支配球-棒转变的平衡常数及热力学函数值。本文检验了梯子模型对TPB体系的适用性, 并对2 M盐介质中TPB胶团的长大具有不同的特征作了讨论。

AN INVESTIGATI ON THE MICELLAR GROWTH IN AQUEOUS TETRADECYLPYRIDINIUM BROMIDE SOLUTIONS USING PHOTON CORRELATION SPECTROSCOPY

Measurements of the autocorrelation function of scattered light intensity from aqueous tetradecylpyridinium bromide (TPB) solutions werec arried out to investigate the growth of TPB micelles in high salt (NaBr) concentration media. The mean hydrodynamic radius (R_h) of TPB micelles has been deduced as a function of temperature (15-85 ℃), NaBr concentration (0.5-2.0 M), and detergent concentration(2-21 gdm-3). In general, the size of the micelles increases with increasing salt or detergent concentration and decreasing temperature. A plot of measured R_h vs. relative scattered intensity, compared to theoretical curves corresponding to different model shapes, indicates that the enlarged TPB micelles have a shape of prolate spherocylinders. Based on these R_h measurements, values of the thermodynamic parameter K governing the sphere-to-rod transition are determined. Numerical values of enthalpy and entropy change for this transition on per monomer basis, deduced from the linear plot of lnK vs. 1/T in 0.5 and 1.0 M NaBr, are rather consistent with those of CPB micelles, indicating that these energy parameters are independent of the chain length. In respect to temperature-dependent micellar growth an anomalous behavior that a finite size of about 26.0 nm is asymtemperature has been observed under conditions of higher NaBr concentration (2.0 M). In this case the thermodynamic model of the sphere-to-rod transition is invlid and the possible causes are discussed.