流场驱动的嵌段共聚物过孔动力学行为的模拟研究

The flow-induced polymer translocation through a nanopore has been the subject of much recent study in polymer physics due to its importance in the biomacromolecule sequencing, the separation of polymers with different topologies and the transition between various block copolymer aggregated structures. The study of the flow-induced block copolymer translocation through the nanopore is of great significance, and has important application in the field of the separation of block copolymers and the transition between various block copolymer aggregated structures. Efficient and accurate computer simulation can serve as an effective method to investigate this subject due to the limitations of theory and experiment. However, in the previous studies, most corresponding simulations have focused on the implicit solvent models, which lack the consideration of the system velocity flux and the capture process of polymers. Therefore, we propose to study the flow-induced block copolymer translocation through a nanopore using a hybrid simulation method that incorporates a lattice-Boltzmann approach for the fluid into a molecular dynamics model for the polymer. We intend to systematically investigate the effects of the block length, the hydrophobic interaction, and the interaction between the copolymer and the nanopore on the critical velocity flux of the block copolymer and the block copolymer aggregated structures. We hope our research can provide theoretical support for the development of nanotechnologies based on the separation of block copolymers and the transition between various block copolymer aggregated structures.

随着对生物大分子测序、不同拓扑结构高分子纯化和嵌段共聚物聚集结构调控等纳米技术的需要，流场驱动的高分子穿过纳米孔的输运行为成为了高分子物理研究中一个重要的课题。嵌段共聚物在流场驱动下穿过纳米孔的输运行为不仅有重要的学术价值，而且对应用纳米孔实现嵌段共聚物混合物的分离与表征以及嵌段共聚物聚集结构的调控具有重要的现实意义。高效准确的计算机模拟方法克服了理论和实验方法的诸多限制，成为了研究该课题的强有力工具。为了突破现有隐含溶剂模型无法考虑体系流量和寻孔过程的束缚，本项目拟利用分子动力学和格子玻尔兹曼耦合的杂化模拟方法系统研究流场驱动的单链嵌段共聚物以及嵌段共聚物聚集体穿过纳米孔的动力学行为，重点研究共聚物嵌段长度、溶剂性质、共聚物与纳米孔相互作用等因素对嵌段共聚物临界流量以及聚集结构的影响，为应用纳米孔实现嵌段共聚物混合物的分离与表征以及嵌段共聚物聚集结构的调控提供重要的理论指导。

复杂流场下高分子穿过受限空间的动力学行为一直是高分子领域里基础性的重要课题。本项目利用分子动力学与格子玻尔兹曼耦合的杂化数值模拟方法，从临界流量、输运时间以及构型转变等角度系统研究了流场驱动的嵌段共聚物以及嵌段共聚物胶束穿过受限空间的动力学行为。研究发现，对于相同链长的单链嵌段共聚物，随着疏水嵌段比的增大，嵌段共聚物穿过受限管道的临界流量迅速增加，该结果为实现嵌段共聚物混合物的分离与提纯提供了一种新的解决思路；对于不同嵌段共聚物胶束，其核的尺寸大于管道尺寸时，胶束在穿过受限管道会破裂，并在穿过管道后进行重组，该结论为进一步明确嵌段共聚物胶束在药物输运等领域的应用提供了前瞻性的计算依据。此外，结合标度理论，系统阐释了高分子在相反流场下逃离受限管道时反临界流量的物理机制，其代表了受限自由能和流体力学作用力的平衡，并进一步建立了复杂流场下高分子囊泡穿过受限空间的有限元模型，发现输运过程中应变能呈现一高一低的双峰分布，高峰对应哑铃形，低峰对应降落伞形，相关研究为实现单分子调控以及微纳尺度结构体的筛选提供了系统可靠的理论指导。