Dynamics of a polymer chain in solution gets significantly affected by the temperature and frictional forces arising due to viscosity of the solvent. Here, using an explicit solvent framework for polymer simulation with the liberty to tune the viscous drag of the system, we study the nonequilibrium dynamics of a flexible homopolymer when it is suddenly quenched from an extended random-coil state in good solvent to poor solvent conditions. Results from our extensive simulations reveal that depending on the temperature T and viscous drag, one encounters long-lived sausage-like intermediates following the usual pearl-necklace intermediates. Using shape factors of the polymer we disentangle these two distinct stages of the overall collapse process. This allows us to extract the corresponding relaxation times and their respective scaling behaviors as a function of the length of the polymer. The relaxation time τ_s of the sausage stage, which is the rate-limiting stage of the overall collapse process, follows an anti-Arrhenius behavior in the high-T limit, and the Arrhenius behavior in the low-T limit. Furthermore, the variation of τ_s with the viscous drag provides evidence of internal friction of the polymer, that modulates the overall collapse significantly, analogous to what is observed for relaxation rates of proteins during their folding. This suggests that the origin of internal friction in proteins is plausibly intrinsic to its polymeric backbone rather than other specifications.

中文翻译：

---

温度和粘度调节聚合物塌陷过程中的中间体


溶液中聚合物链的动力学会受到温度和溶剂粘度引起的摩擦力的显著影响。在这里，使用显式溶剂框架进行聚合物模拟，并自由调整系统的粘性阻力，我们研究了柔性均聚物在良好溶剂条件下突然从扩展无规卷曲状态淬火到不良溶剂条件下的非平衡动力学。我们广泛的模拟结果表明，根据温度 T 和粘性阻力，人们会遇到长寿命的香肠状中间体，紧随通常的珍珠项链中间体。利用聚合物的形状因子，我们解开了整个塌陷过程的这两个不同阶段。这使我们能够提取相应的弛豫时间及其各自的缩放行为作为聚合物长度的函数。香肠阶段的弛豫时间 τ_s，即整个坍缩过程的限速阶段，在高 T 极限下遵循反 Arrhenius 行为，在低 T 极限下遵循 Arrhenius 行为。此外，τ_s 随粘性阻力的变化提供了聚合物内摩擦的证据，这显着调节了整体塌陷，类似于观察到的蛋白质在折叠过程中的弛豫速率。这表明蛋白质中内耗的起源似乎是其聚合物骨架所固有的，而不是其他规格。