动态光散射法研究季铵盐Gemini表面活性剂的胶团化行为

用动态光散射技术在10～70℃温度范围内,通过测定胶团的平均流体力学半径随温度、盐浓度和联接基团长度的变化情况,研究联接基团为聚亚甲基链的阳离子季铵盐Gemini表面活性剂胶团在无机盐介质中的长大规律.实验结果表明,增加盐量、降低温度和减小联接基团的长度均使平均流体力学半径变大,Gemini表面活性剂胶团长大时是由球状转变为棒状.从实验测定的平流体力学半径求算了支配球-棒转变的平衡常数及热力学函数值,并用NNLS(non-negatively constrainedleast square)算法对胶团的粒径分布情况进行了分析.此外,对具有短联接基团的Gemini表面活性剂胶团长大所具有的独特性质进行了讨论.

Micellar Growth of Quaternary Ammonium Gemini Surfactant in Aqueous Solutions Using Dynamic Light Scattering

The micellar growth of quaternary ammonium Gemini surfactants containing methylene group spacer (referred to as C 12-s-C 12, 2Br) in inorganic salt (NaBr) media was investigated by using dynamic light scattering. The size of micelles increases with increasing salt concentration or decreasing temperature or decreasing the length of spacer chain. The enlarged micelles have a shape of prolate ellipsoid or rod. Based on these mean hydrodynamic radius (R h) measurements, values of the thermodynamic parameter K governing the sphere to rod transition were determined. Numerical values of enthalpy and entropy change for this transition were deduced from the linear plot of ln K vs. 1/T. The novel micellar growth of C 12-2-C 12, 2Br was discussed. The distribution of micelle size was analyzed by using non-negatively constrained least square (NNLS) algorithm.