Garnier Sébastien, Laschewsky André
Universität Potsdam, P.O Box 601553, D-14415 Potsdam-Golm, Germany.
Langmuir. 2006 Apr 25;22(9):4044-53. doi: 10.1021/la0600595.
Several series of amphiphilic diblock copolymers are investigated as macrosurfactants in comparison to reference low-molar-mass and polymeric surfactants. The various copolymers share poly(butyl acrylate) as a common hydrophobic block but are distinguished by six different hydrophilic blocks (one anionic, one cationic, and four nonionic hydrophilic blocks) with various compositions. Dynamic light scattering experiments indicate the presence of micelles over the whole concentration range from 10(-4) to 10 g x L(-1). Accordingly, the critical micellization concentrations are very low. Still, the surface tension of aqueous solutions of block copolymers decreases slowly but continuously with increasing concentration, without exhibiting a plateau. The longer the hydrophobic block, the shorter the hydrophilic block, and the less hydrophilic the monomer of the hydrophilic block is, the lower the surface tension is. However, the effects are small, and the copolymers reduce the surface tension much less than standard low-molar-mass surfactants. Also, the copolymers foam much less and even act as anti-foaming agents in classical foaming systems composed of standard surfactants. The copolymers stabilize O/W emulsions made of methyl palmitate as equally well as standard surfactants but are less efficient for O/W emulsions made of tributyrine. However, the copolymer micelles exhibit a high solubilization power for hydrophobic dyes, probably at their core-corona interface, in dependence on the initial geometry of the micelles and the composition of the block copolymers. Whereas micelles of copolymers with strongly hydrophilic blocks are stable upon solubilization, solubilization-induced micellar growth is observed for copolymers with moderately hydrophilic blocks.
与参考低摩尔质量和聚合物表面活性剂相比，研究了几系列两亲性二嵌段共聚物作为大分子表面活性剂。各种共聚物都有聚（丙烯酸丁酯）作为共同的疏水嵌段，但通过六种不同的亲水嵌段（一种阴离子、一种阳离子和四种非离子亲水嵌段）以及不同的组成来区分。动态光散射实验表明，在10^(-4)至10 g·L^(-1)的整个浓度范围内都存在胶束。因此，临界胶束浓度非常低。尽管如此，嵌段共聚物水溶液的表面张力随着浓度的增加而缓慢但持续下降，没有出现平台期。疏水嵌段越长、亲水嵌段越短以及亲水嵌段的单体亲水性越低，表面张力就越低。然而，这些影响很小，并且共聚物降低表面张力的程度远小于标准低摩尔质量表面活性剂。此外，共聚物的泡沫少得多，甚至在由标准表面活性剂组成的经典发泡体系中起到消泡剂的作用。这些共聚物对由棕榈酸甲酯制成的水包油乳液的稳定效果与标准表面活性剂相当，但对由三丁酸甘油酯制成的水包油乳液的效率较低。然而，共聚物胶束对疏水性染料具有很高的增溶能力，可能是在其核 - 冠界面处，这取决于胶束的初始几何形状和嵌段共聚物的组成。具有强亲水嵌段的共聚物胶束在增溶时是稳定的，而对于具有中等亲水嵌段的共聚物则观察到增溶诱导的胶束生长。
