Park Soo-Young, Park Myeong-Hye
Department of Polymer Science, Kyungpook National University, #1370 Sangyuk-dong, Buk-gu, Daegu 702-701, Korea.
Langmuir. 2007 Jun 5;23(12):6788-95. doi: 10.1021/la070104o. Epub 2007 May 8.
PI cores of the micelles of poly(styrene-b-isoprene) (PS-b-PI) diblock copolymers, in PS selective solvents, were cross-linked with sulfur monochloride (S2Cl2). The cross-linked micellar structure was maintained after dialysis in THF (neutral solvent) and did not change during heating. Cross-linking brought about the opportunity for TEM images in a solution state; otherwise, the micellar structure would be destroyed (or changed) during the evaporation of the solvent on a carbon-coated copper grid. The Flory interaction parameter, chi, between the PI block and the solvent was controlled by mixing two selective solvents (DMP/toluene, DMP/DEP and DEP/DBP) which have different degrees of selectivity for the PS block, as well as heating the solutions. Two block copolymers, PS(7.2K)-b-PI(7.8K) and PS(5.5K)-b-PI(18.8K), were studied in order to clarify the effects of the relative chain length of each block on the micelle structure in the selective solvents. PS(7.2K)-b-PI(7.8K), which is nearly symmetric, showed only spherical micelles in the DMP/toluene mixture. The basic spherical micellar shape of PS(7.2K)-b-PI(7.8K) did not change with chi, while the size and aggregation number of the micelles increased as chi increased until 2.05 and then were saturated after that. PS(5.5K)-b-PI(18.8K), which is asymmetric, showed a structural change from spherical to cylindrical to vesicular micelles with an increase in the selectivity of the DMP/DEP and DEP/DBP mixtures (which was also confirmed by TEM and SAXS studies). Giant vesicular micelles with a diameter of approximately 2.5 microm were observed in high-selectivity solvents. The size of the vesicular micelle seemed to decrease as selectivity decreased. The systematic changes of the micellar structures of PS(5.5K)-b-PI(18.8K), via changes in solvent selectivity, could be demonstrated through TEM images, which were prepared by evaporating the solvent of the cross-linked micellar solution onto the carbon-coated grid after dialysis.
在聚苯乙烯选择性溶剂中，聚（苯乙烯 - b - 异戊二烯）（PS - b - PI）二嵌段共聚物胶束的PI核用二氯化硫（S₂Cl₂）进行交联。在四氢呋喃（中性溶剂）中透析后，交联的胶束结构得以保持，并且在加热过程中不会改变。交联为溶液状态下的透射电子显微镜（TEM）成像创造了条件；否则，在涂碳铜网上溶剂蒸发过程中，胶束结构将会被破坏（或改变）。通过混合两种对PS嵌段具有不同选择性程度的选择性溶剂（二甲基亚砜/甲苯、二甲基亚砜/二乙基亚砜和二乙基亚砜/邻苯二甲酸二丁酯）以及加热溶液，来控制PI嵌段与溶剂之间的弗洛里相互作用参数χ。研究了两种嵌段共聚物PS(7.2K)-b-PI(7.8K)和PS(5.5K)-b-PI(18.8K)，以阐明每个嵌段的相对链长对选择性溶剂中胶束结构的影响。几乎对称的PS(7.2K)-b-PI(7.8K)在二甲基亚砜/甲苯混合物中仅呈现球形胶束。PS(7.2K)-b-PI(7.8K)的基本球形胶束形状不随χ变化，而胶束的尺寸和聚集数随着χ增加至2.05而增大，之后达到饱和。不对称的PS(5.5K)-b-PI(18.8K)随着二甲基亚砜/二乙基亚砜和二乙基亚砜/邻苯二甲酸二丁酯混合物选择性的增加，呈现从球形到圆柱形再到囊泡状胶束的结构变化（这也通过TEM和小角X射线散射（SAXS）研究得到证实）。在高选择性溶剂中观察到直径约为2.5微米的巨型囊泡状胶束。囊泡状胶束的尺寸似乎随着选择性降低而减小。通过TEM图像可以证明，PS(5.5K)-b-PI(18.8K)胶束结构通过溶剂选择性的变化而发生的系统变化，这些图像是在透析后将交联胶束溶液的溶剂蒸发到涂碳网格上制备得到的。
