Division of Physical Chemistry, Department of Chemistry, Center for Chemistry and Chemical Engineering, Lund University, Post Office Box 124, SE-221 00 Lund, Sweden.
Langmuir. 2012 Dec 4;28(48):16536-46. doi: 10.1021/la303938k. Epub 2012 Nov 15.
Nanoparticles with an internal structure have been prepared by dispersing under dilute conditions poly(acrylic acid) with a polymerization degree n = 6000 (PAA6000) together with a cationic surfactant hexadecyltrimethylammonium hydroxide (C16TAOH) and the non-ionic surfactant penta(ethylene glycol) monododecyl ether (C12E5) in water. The nanoparticles are formed at different mixing ratios in the corresponding two-phase regions (liquid crystalline phase/dilute isotropic phase) of the C16TAPA6000 complex salt/C12E5/water ternary phase diagram. The particles consist of polyacrylate PA6000– polyions, C16TA+ surfactant ions, and C12E5. Their internal ordering was identified by small-angle X-ray scattering (SAXS) to be either bicontinuous cubic with the Ia3d crystallographic space group or normal hexagonal depending upon the amount of C12E5. The bicontinuous cubic phase, to our knowledge never observed before in polyelectrolyte–surfactant particle systems, was inferred by SAXS experiments. The data also showed that this structure is thermoresponsive in a reversible manner. The bicontinuous cubic space group transforms from Ia3d to Im3m as the temperature decreases from 25 to 15 °C. According to dynamic light scattering and electrophoretic mobility measurements, the particles have a well-defined size (apparent hydrodynamic radii RH in the range of 88–140 nm) and carry a positive net charge. The size of the nanoparticles is stable up to 1 month. The faceted nanoparticles are visualized by cryogenic transmission electron microscopy that also reveals their coexistence with thread-like C12E5 micelles.
通过在稀溶液条件下分散具有聚合度 n = 6000 的聚（丙烯酸）（PAA6000），与阳离子表面活性剂十六烷基三甲基氢氧化铵（C16TAOH）和非离子表面活性剂五（乙二醇）单十二醚（C12E5）一起，制备了具有内部结构的纳米粒子。纳米粒子在相应的两相区（液晶相/稀各向同性相）中以不同的混合比形成于 C16TAPA6000 复合盐/C12E5/水三元相图中。这些粒子由聚丙烯酸 PA6000-聚离子、C16TA+表面活性剂离子和 C12E5 组成。它们的内部有序性通过小角 X 射线散射（SAXS）确定为立方双连续结构，具有 Ia3d 晶体空间群或正常六方结构，具体取决于 C12E5 的量。这种立方双连续相是通过 SAXS 实验推断出来的，据我们所知，这种结构以前从未在聚电解质-表面活性剂粒子系统中观察到过。该数据还表明，这种结构具有可逆的热响应性。当温度从 25°C 降至 15°C 时，立方双连续空间群从 Ia3d 转变为 Im3m。根据动态光散射和电泳迁移率测量，这些粒子具有明确的尺寸（表观水动力半径 RH 在 88-140nm 范围内），并带有正净电荷。纳米粒子的尺寸稳定长达 1 个月。低温透射电子显微镜可视化了这些具有面心立方结构的纳米粒子，同时还揭示了它们与线状 C12E5 胶束的共存。
