论文标题

布朗运动的灵活连接胶体环的运动

Brownian motion of flexibly-linked colloidal rings

论文作者

Verweij, Ruben, Melio, Julio, Chakraborty, Indrani, Kraft, Daniela J

论文摘要

与线性聚合物相比,环或环状聚合物具有独特的特性,因为它们的拓扑封闭结构没有开始或末端。分子环聚合物的实验测量由于其在分子量中的多分散性以及存在不希望的副产物(例如链)而具有挑战性。在这里,我们研究了一个用于环状聚合物的实验模型系统,该模型由柔性链接的微米大小的胶体和$ n $ = 4..8段组成。我们表征了这些柔性胶体环的构象,并发现它们是自由连接到空间限制的。我们测量其扩散行为,并将其与流体动力模拟进行比较。有趣的是,与胶体链相比,柔性胶体环具有更大的平移和旋转扩散系数。与链条相反,它们的内部变形模式显示出$ n \ lyssim 8 $的波动较慢,并且较高的$ n $值饱和。我们表明,源自环结构的约束导致小$ n $的灵活性下降,并推断灵活性的预期缩放为环大小的功能。我们的发现可能对合成和生物环聚合物的行为以及软盘胶体材料的动态模式有影响。

Ring, or cyclic, polymers have unique properties compared to linear polymers, due to their topologically closed structure that has no beginning or end. Experimental measurements on molecular ring polymers are challenging due to their polydispersity in molecular weight and the presence of undesired side products such as chains. Here, we study an experimental model system for cyclic polymers, that consists of rings of flexibly-linked micron-sized colloids with $n$=4..8 segments. We characterize the conformations of these flexible colloidal rings and find that they are freely-jointed up to steric restrictions. We measure their diffusive behavior and compare it to hydrodynamic simulations. Interestingly, flexible colloidal rings have a larger translational and rotational diffusion coefficient compared to colloidal chains. In contrast to chains, their internal deformation mode shows slower fluctuations for $n\lesssim 8$ and saturates for higher values of $n$. We show that constraints stemming from the ring structure cause this decrease in flexibility for small $n$ and infer the expected scaling of the flexibility as function of ring size. Our findings could have implications for the behavior of both synthetic and biological ring polymers, as well as for the dynamic modes of floppy colloidal materials.

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