Seeger Sarah C, Dorfman Kevin D, Lodge Timothy P
Department of Chemical Engineering and Materials Science, University of Minnesota - Twin Cities, Minneapolis, Minnesota 55455, United States.
Department of Chemistry, University of Minnesota - Twin Cities, Minneapolis, Minnesota 55455, United States.
ACS Macro Lett. 2021 Dec 21;10(12):1570-1575. doi: 10.1021/acsmacrolett.1c00508. Epub 2021 Nov 21.
We use umbrella sampling to compute the free energy trajectory of a single chain undergoing expulsion from an isolated diblock copolymer micelle. This approach elucidates the experimentally unobservable transition state, identifies the spatial position of the maximum free energy, and reveals the chain conformation of a single chain as it undergoes expulsion. Combining umbrella sampling with dissipative particle dynamics simulations of AB micelles reveals that the core block (A) of the expelled chain remains partially stretched at the transition state, in contrast with the collapsed state assumed in some previous models. The free energy barrier increases linearly with the Flory-Huggins interaction parameter χ up to large interaction energies, where the structure of the otherwise spherical core apparently deforms near the transition state.
我们使用伞形抽样来计算单链从孤立的双嵌段共聚物胶束中排出时的自由能轨迹。这种方法阐明了实验中无法观察到的过渡态，确定了最大自由能的空间位置，并揭示了单链排出过程中的链构象。将伞形抽样与AB胶束的耗散粒子动力学模拟相结合，结果表明，与之前一些模型中假设的塌陷状态不同，排出链的核嵌段（A）在过渡态时仍部分伸展。自由能垒随弗洛里-哈金斯相互作用参数χ线性增加，直至达到较大的相互作用能，此时原本呈球形的核结构在过渡态附近明显变形。
