Department of Chemical Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
J Colloid Interface Sci. 2010 Apr 1;344(1):81-9. doi: 10.1016/j.jcis.2009.12.049. Epub 2009 Dec 28.
Novel hydrophilic triblock copolymers which form micelles in aqueous solution were studied by static and dynamic light scattering (SLS and DLS), small angle neutron scattering (SANS) and densitometry. The polymers were symmetric A-B-A block copolymers having two poly(ethylene oxide) (PEO) tail blocks and a polyurethane (PU) center segment that contained pendant carboxylic acids. The aggregation number of the micelles decreased with increasing PEO mass content. When attempting to fit the SANS data it was found that no single model was suitable over the entire range of block lengths and PEO mass concentrations investigated here. For the polymer with the highest aggregation number, the data were fitted with a triblock model consisting of a homogeneous core with a corona of non-interacting Gaussian chains for which only two free parameters were required: the radius of the core and the radius of gyration of the corona. In this case, the core was found to be effectively dry. At lower aggregation numbers, a star polymer model generated significantly better fits, suggesting the absence of any identifiable central core structure. Good agreement was found between the sizes measured by DLS, SANS and theoretical predictions of micelle size from a density distribution theory. These results show that when significant changes in aggregation number occur, the nanostructure of the micelle can change substantially even for polymers that are remarkably similar.
新型亲水性三嵌段共聚物在水溶液中形成胶束，通过静态和动态光散射（SLS 和 DLS）、小角中子散射（SANS）和密度测定法进行了研究。这些聚合物是对称的 A-B-A 嵌段共聚物，具有两个聚（氧化乙烯）（PEO）尾链和一个含有侧挂羧酸的聚氨酯（PU）中心链段。胶束的聚集数随 PEO 质量含量的增加而减少。在尝试拟合 SANS 数据时发现，没有一个单一的模型适用于此处研究的整个嵌段长度和 PEO 质量浓度范围。对于具有最高聚集数的聚合物，数据采用由均匀核和非相互作用高斯链的冕组成的三嵌段模型进行拟合，该模型仅需要两个自由参数：核的半径和冕的回转半径。在这种情况下，发现核实际上是干燥的。在较低的聚集数下，星形聚合物模型产生了更好的拟合，表明不存在任何可识别的中心核结构。通过 DLS、SANS 和密度分布理论预测的胶束尺寸之间的良好一致性表明，即使对于非常相似的聚合物，当聚集数发生显著变化时，胶束的纳米结构也会发生实质性变化。
