Lang Philipp, Frey Erwin
Arnold-Sommerfeld-Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, D-80333, München, Germany.
Nat Commun. 2018 Feb 5;9(1):494. doi: 10.1038/s41467-018-02837-5.
Reptation theory has been highly successful in explaining the unusual material properties of entangled polymer solutions. It reduces the complex many-body dynamics to a single-polymer description, where each polymer is envisaged to be confined to a tube through which it moves in a snake-like fashion. For flexible polymers, reptation theory has been amply confirmed by both experiments and simulations. In contrast, for semiflexible polymers, experimental and numerical tests are either limited to the onset of reptation, or were performed for tracer polymers in a fixed, static matrix. Here, we report Brownian dynamics simulations of entangled solutions of semiflexible polymers, which show that curvilinear motion along a tube (reptation) is no longer the dominant mode of dynamics. Instead, we find that polymers disentangle due to correlated constraint release, which leads to equilibration of internal bending modes before polymers diffuse the full tube length. The physical mechanism underlying terminal stress relaxation is rotational diffusion mediated by disentanglement rather than curvilinear motion along a tube.
蛇行理论在解释缠结聚合物溶液的异常材料特性方面取得了巨大成功。它将复杂的多体动力学简化为单聚合物描述，其中每个聚合物被设想限制在一个管中，并以蛇形方式在管中移动。对于柔性聚合物，蛇行理论已被实验和模拟充分证实。相比之下，对于半柔性聚合物，实验和数值测试要么仅限于蛇行的起始阶段，要么是针对固定静态基质中的示踪聚合物进行的。在这里，我们报告了半柔性聚合物缠结溶液的布朗动力学模拟，结果表明沿管的曲线运动（蛇行）不再是主要的动力学模式。相反，我们发现聚合物由于相关的约束释放而解缠结，这导致聚合物在扩散整个管长之前内部弯曲模式达到平衡。终端应力松弛背后的物理机制是由解缠结介导的旋转扩散，而不是沿管的曲线运动。
