The non-free draining effect for small cyclics in solution
The non-free draining effect for small cyclics in solution
复制标题
溶液中小环的非自由排水效应
DOI：
10.1016/j.polymer.2020.123202
复制
发表时间：
2020-11
期刊：
影响因子：
4.6
通讯作者：
Chang Taihyun
中科院分区：
文献类型：
--
作者：
Zhao Yiming;Gao Lingfeng;Lu Huanjun;Li Xiaohong;Tu Yingfeng;Chang Taihyun
通常认为，由于约束拓扑结构，环状聚合物具有比其线性对应物更小的流体动力学半径（Rhs）。这种共识是基于高分子量（MW）聚合物的结果，其中链被认为是线圈。利用扩散有序核磁共振技术研究了低分子量环状聚苯乙烯（3000 ~ 11，000）、环状烷烃及其线性对应物的Rhs，首次发现了小分子环状物的非自由排液效应，即溶剂分子通过环的消耗导致流体力学尺寸的增加.随着聚合物分子量的减小，这种影响变得更加显著，环状聚苯乙烯的Rhs接近线性聚苯乙烯。在MW约660处的交叉点以下，环状聚苯乙烯的Rhs大于从所建立的标度律得到的线性对应物。这是由观察到的现象，环烷烃具有largerRhs比他们的正烷烃对应物支持。研究结果有助于理解小分子环状化合物在溶液中的热力学行为，特别是生命科学中具有生物活性的小分子环状化合物。
It is commonly believed that cyclic polymers have smaller hydrodynamic radii (Rhs) than their linear counterparts due to the constraint topology. This consensus is based on the results from polymers with high molecular weights (MWs), where the chains are considered as coils. Herein, we investigate theRhs of low MW cyclic polystyrenes (3000–11,000), cyclic alkanes and their linear counterparts by diffusion ordered NMR spectroscopy.For the first time, a non-free draining effect for small cyclics is revealed, due to the depletion of solvent molecules to pass through the rings, which leads to the increment of hydrodynamic size. With the decrement of polymer MW, this effect becomes more significant andRhs of cyclic polystyrenes approach that of their linear counterparts. Below a crossover point at MW around 660,Rhs of cyclic polystyrenes are larger than their linear counterparts from the established scaling laws. This is supported by the observed phenomena that cycloalkanes have largerRhs than theirn-alkane counterparts. The results are helpful in understanding the thermodynamic behaviors of small cyclics in solution, especially those bioactive small ring molecules in life science.
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