AI 中文总结
本研究通过朗之万动力学、元动力学模拟及福克-普朗克模型，探究了电压驱动下线性与三臂星形聚合物跨纳米孔的转运热力学与动力学，明确了三臂星形聚合物转运的阈值电压特性及相关影响因素。
AI 中文摘要
本研究探究了电压驱动下均匀带电的长链线性聚合物与三臂星形聚合物通过窄纳米孔的转运过程，采用聚合物的粗粒化模型与纳米孔的半隐式表示开展朗之万动力学模拟。研究发现，在较宽的电压范围内，线性聚合物的平均转运时间与施加电压成反比；而相同分子量的三臂星形聚合物的平均转运时间，在低于阈值电压时会显著偏离该标度关系。阈值电压几乎不依赖于聚合物的分子量，但与纳米孔尺寸和盐浓度相关。采用元动力学模拟估算三臂星形聚合物转运的自由能景观，结果显示，在阈值电压以下，自由能存在一个显著的第二势垒，源于拖尾臂在纳米孔内的链段间熵贡献与静电相互作用。基于估算的自由能构建的福克-普朗克模型，可准确预测阈值电压以下对标度关系的偏离，且使用与电压无关的拟合参数时，与朗之万动力学模拟结果表现出显著一致性，该一致性在不同纳米孔半径、聚合物分子量及盐浓度的研究中均成立。此外，本研究提出了自由能景观的简单扩展方案，无需额外计算成本高昂的模拟即可预测更高分子量聚合物的转运动力学。
英文摘要
In this work, voltage-driven translocation of uniformly charged long linear and three-arm star polymers through narrow nanopores is investigated. Langevin dynamics simulation is performed using a coarse-grained model of the polymer and a semi-implicit representation of the nanopore. The mean translocation time of a linear polymer is found to be inversely proportional to the applied voltage over a wide range of voltages. In contrast, the mean translocation time of a three-arm star polymer of the same molecular weight exhibits a pronounced deviation from this scaling relation below a threshold voltage. The threshold voltage is found to be nearly independent of the molecular weight of the polymer, but depends on the size of the nanopore and salt concentration. Metadynamics simulation is used to estimate the free-energy landscape for the translocation of the three-arm star polymer. Below the threshold voltage, the free energy exhibits a pronounced second barrier resulting from an entropic contribution and electrostatic interactions between segments of the trailing arm inside the nanopore. A Fokker-Planck model developed using the estimated free-energy accurately predicts the deviation from the scaling relation below the threshold voltage and shows a remarkable agreement with the Langevin dynamics simulation results using a voltage-independent fitting parameter. The agreement between the theory and the Langevin dynamics simulation results is seen for different nanopore radii, molecular weights of the polymer and salt concentrations studied. A simple extension of the free energy landscape is suggested to predict translocation kinetics for higher molecular weights of the polymer without performing additional computationally expensive simulations.
CommentsSupplementary document (SI.pdf) and supplementary video (translocation.mp4)
