Sommer Cornelia, Pedersen Jan Skov, Garamus Vasil M
Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Langmuir. 2005 Mar 15;21(6):2137-49. doi: 10.1021/la047489k.
Spherical micelles of the diblock copolymer/surfactant Brij 700 (C(18)EO(100)) in water (D(2)O) solution have been investigated by small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). SAXS and SANS experiments are combined to obtain complementary information from the two different contrast conditions of the two techniques. Solutions in a concentration range from 0.25 to 10 wt % and at temperatures from 10 to 80 degrees C have been investigated. The data have been analyzed on absolute scale using a model based on Monte Carlo simulations, where the micelles have a spherical homogeneous core with a graded interface surrounded by a corona of self-avoiding, semiflexible interacting chains. SANS and SAXS data were fitted simultaneously, which allows one to obtain extensive quantitative information on the structure and profile of the core and corona, the chain interactions, and the concentration effects. The model describes the scattering data very well, when part of the EO chains are taken as a "background"contribution belonging to the solvent. The effect of this becomes non-negligible at polymer concentrations as low as 2 wt %, where overlap of the micellar coronas sets in. The results from the analysis on the micellar structure, interchain interactions, and structure factor effects are all consistent with a decrease in solvent quality of water for the PEO block as the theta temperature of PEO is approached.
通过小角X射线散射（SAXS）和小角中子散射（SANS）研究了两嵌段共聚物/表面活性剂Brij 700（C(18)EO(100)）在水（D(2)O）溶液中的球形胶束。SAXS和SANS实验相结合，从这两种技术的两种不同对比条件中获取互补信息。研究了浓度范围为0.25至10 wt%且温度为10至80摄氏度的溶液。使用基于蒙特卡罗模拟的模型在绝对尺度上对数据进行了分析，其中胶束具有球形均匀核，其界面渐变，周围是自回避、半柔性相互作用链的冠层。同时对SANS和SAXS数据进行拟合，这使得人们能够获得关于核和冠层的结构与轮廓、链相互作用以及浓度效应的广泛定量信息。当部分EO链被视为属于溶剂的“背景”贡献时，该模型能很好地描述散射数据。在聚合物浓度低至2 wt%时，这种影响变得不可忽略，此时胶束冠层开始重叠。关于胶束结构、链间相互作用和结构因子效应的分析结果都与随着接近PEO的θ温度，水对PEO嵌段的溶剂质量下降相一致。
