Theoretical Physics of Living Matter, Institute for Advanced Simulation and Institute of Biological Information Processing, Forschungszentrum Jülich, D-52425 Jülich, Germany.
J Chem Phys. 2021 Jul 28;155(4):044902. doi: 10.1063/5.0058150.
The conformational and dynamical properties of a passive polymer embedded in a bath of active Brownian particles (ABPs) are studied by Langevin dynamics simulations. Various activities and ABP concentrations below and above the critical values for motility-induced phase separation (MIPS) are considered. In a homogeneous ABP fluid, the embedded polymer swells with increasing bath activity, with stronger swelling for larger densities. The polymer dynamics is enhanced, with the diffusion coefficient increasing by a power-law with increasing activity, where the exponent depends on the ABP concentration. For ABP concentrations in the MIPS regime, we observe a localization of the polymer in the low-density ABP phase associated with polymer collapse for moderate activities and a reswelling for high activities accompanied by a preferred localization in the high-density ABP phase. Localization and reswelling are independent of the polymer stiffness, with stiff polymers behaving similarly to flexible polymers. The polymer collapse is associated with a slowdown of its dynamics and a significantly smaller center-of-mass diffusion coefficient. In general, the polymer dynamics can only partially be described by an effective (bath) temperature. Moreover, the properties of a polymer embedded in a homogeneous active bath deviate quantitatively from those of a polymer composed of active monomers, i.e., linear chains of ABPs; however, such a polymer exhibits qualitatively similar activity-dependent features.
通过朗之万动力学模拟研究了嵌入在活性布朗粒子（ABP）浴中的无规聚合物的构象和动力学性质。考虑了低于和高于流动性诱导相分离（MIPS）临界值的各种活性和 ABP 浓度。在均匀的 ABP 流体中，随着浴活性的增加，嵌入的聚合物会溶胀，密度越大，溶胀越强。聚合物的动力学增强，扩散系数随活性呈幂律增加，指数取决于 ABP 浓度。对于 MIPS 区的 ABP 浓度，我们观察到聚合物在低密度 ABP 相中的定位与中等活性下的聚合物坍塌以及高活性下的再溶胀有关，同时聚合物优先定位在高密度 ABP 相中。定位和再溶胀与聚合物的刚度无关，刚性聚合物的行为与柔性聚合物相似。聚合物的坍塌与动力学的减缓以及质心扩散系数的显著减小有关。一般来说，聚合物的动力学只能通过有效（浴）温度部分描述。此外，嵌入在均匀活性浴中的聚合物的性质与由活性单体组成的聚合物（即 ABP 的线性链）定量不同；然而，这种聚合物表现出定性上相似的活性依赖性特征。
