Early Julia T, Yager Kevin G, Lodge Timothy P
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
ACS Macro Lett. 2020 May 19;9(5):756-761. doi: 10.1021/acsmacrolett.0c00273. Epub 2020 May 6.
Recently, attention has been directed toward understanding the dynamics and relaxation kinetics of block copolymer micelles, including mechanisms such as micelle fragmentation and fusion. The few prior studies on block copolymer micelle fragmentation relied on ensemble averaging techniques such as small-angle X-ray scattering and dynamic light scattering; some individual particles were imaged by ex situ transmission electron microscopy. Here we report the direct observation of fragmentation for three molecular weights of 1,2-polybutadiene--poly(ethylene oxide) (PB-PEO) micelles in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide using high-temperature liquid-phase transmission electron microscopy (LP-TEM). The use of in situ LP-TEM provides unique insights into the evolution of block copolymer micelles during fragmentation. Specifically, upon heating to 170 °C, a sequence of morphological transitions from a spherical micelle to a prolate ellipsoid, then a "peanut" shape, followed by a two-spherical-compartment micelle was observed, where the last is presumed to be the transition state.
最近，人们的注意力已转向了解嵌段共聚物胶束的动力学和弛豫动力学，包括胶束破碎和融合等机制。之前关于嵌段共聚物胶束破碎的少数研究依赖于小角X射线散射和动态光散射等系综平均技术；一些单个颗粒通过非原位透射电子显微镜成像。在此，我们报告了使用高温液相透射电子显微镜（LP-TEM）在离子液体1-乙基-3-甲基咪唑双（三氟甲基磺酰）亚胺中对三种分子量的1,2-聚丁二烯-聚（环氧乙烷）（PB-PEO）胶束破碎的直接观察。原位LP-TEM的使用为嵌段共聚物胶束在破碎过程中的演变提供了独特的见解。具体而言，加热到170°C时，观察到一系列形态转变，从球形胶束到长椭球体，然后是“花生”形状，接着是双球形隔室胶束，其中最后一种被认为是过渡态。
