Jansson Jörgen, Schillén Karin, Nilsson Markus, Söderman Olle, Fritz Gerhard, Bergmann Alexander, Glatter Otto
Physical Chemistry 1, Chemical Center, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
J Phys Chem B. 2005 Apr 21;109(15):7073-83. doi: 10.1021/jp0468354.
The formation of triblock copolymer/surfactant complexes upon mixing a nonionic Pluronic polymer (PEO-PPO-PEO) with a cationic surfactant, hexadecyltrimethylammonium chloride (CTAC), has been studied in dilute aqueous solutions using small-angle X-ray scattering, static and dynamic light scattering, and self-diffusion NMR. The studied copolymer (denoted P123, EO(20)PO(68)EO(20)) forms micelles with a radius of 10 nm and a molecular weight of 7.5 x 10(5), composed of a hydrophobic PPO-rich core of radius 4 nm and a water swollen PEO corona. The P123/CTAC system has been investigated between 1 and 5 wt % P123 and with varying surfactant concentration up to approximately 170 mM CTAC (or a molar ratio n(CTAC)/n(P123) = 19.3). When CTAC is mixed with micellar P123 solutions, two different types of complexes are observed at various CTAC concentrations. At low molar ratios (>/=0.5) a "P123 micelle-CTAC" complex is obtained as the CTAC monomers associate noncooperatively with the P123 micelle, forming a spherical complex. Here, an increased interaction between the complexes with increasing CTAC concentration is observed. The interaction has been investigated by determining the structure factor obtained by using the generalized indirect Fourier transformation (GIFT) method. The interaction between the P123 micelle-CTAC complexes was modeled using the Percus-Yevick closure. For the low molar ratios a small decrease in the apparent molecular weight of the complex was obtained, whereas the major effect was the increase in electrostatic repulsion between the complexes. Between molar ratios 1.9 and 9 two coexisting complexes were found, one P123 micelle-CTAC complex and one "CTAC-P123" complex. The latter one consists of one or a few P123 unimers and a few CTAC monomers. As the CTAC concentration increases above a molar ratio of 9, the P123 micelles are broken up and only the CTAC-P123 complex that is slightly smaller than a CTAC micelle exists. The interaction between the P123/CTAC complexes was modeled with the hypernetted-chain closure using a Yukawa type potential in the GIFT analysis, due to the stronger electrostatic repulsion.
通过小角X射线散射、静态和动态光散射以及自扩散核磁共振技术，研究了在稀水溶液中，非离子型普朗尼克聚合物（PEO-PPO-PEO）与阳离子表面活性剂十六烷基三甲基氯化铵（CTAC）混合时三嵌段共聚物/表面活性剂复合物的形成。所研究的共聚物（记为P123，EO(20)PO(68)EO(20)）形成半径为10 nm、分子量为7.5×10(5)的胶束，由半径为4 nm的富含PPO的疏水核和水溶胀的PEO冠组成。对P123/CTAC体系进行了研究，P123的浓度为1至5 wt%，表面活性剂浓度变化范围高达约170 mM CTAC（或摩尔比n(CTAC)/n(P123)=19.3）。当CTAC与胶束状P123溶液混合时，在不同CTAC浓度下观察到两种不同类型的复合物。在低摩尔比（≥0.5）时，随着CTAC单体与P123胶束非协同缔合，形成一种“P123胶束-CTAC”复合物，形成球形复合物。在此，观察到随着CTAC浓度增加，复合物之间的相互作用增强。通过使用广义间接傅里叶变换（GIFT）方法确定结构因子来研究这种相互作用。使用Percus-Yevick封闭模型对P123胶束-CTAC复合物之间的相互作用进行建模。对于低摩尔比，复合物的表观分子量略有下降，而主要影响是复合物之间静电排斥力的增加。在摩尔比1.9至9之间，发现两种共存的复合物，一种是P123胶束-CTAC复合物，另一种是“CTAC-P123”复合物。后者由一个或几个P123单聚物和几个CTAC单体组成。当CTAC浓度增加到摩尔比大于9时，P123胶束被破坏，仅存在略小于CTAC胶束的CTAC-P123复合物。由于静电排斥力更强，在GIFT分析中使用Yukawa型势，用超网链封闭模型对P123/CTAC复合物之间的相互作用进行建模。
