Unexpected power-law stress relaxation of entangled ring polymers.
Unexpected power-law stress relaxation of entangled ring polymers.
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DOI：
10.1038/nmat2292
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发表时间：
2008-12
期刊：
影响因子：
41.2
通讯作者：
Rubinstein M
中科院分区：
文献类型：
--
作者：
Kapnistos M;Lang M;Vlassopoulos D;Pyckhout-Hintzen W;Richter D;Cho D;Chang T;Rubinstein M
经过多年的深入研究，纠缠聚合物运动的大多数方面已经被理解。长的线性和支化聚合物具有特征缠结平台，并且它们的应力分别通过链蠕动或分支收缩而松弛。在这两种机制中，链端的存在是必不可少的。但是没有末端的缠结聚合物是如何放松它们的应力的呢？使用适当纯化的高摩尔质量环聚合物，我们证明，这些材料表现出自相似的动力学，产生幂律应力松弛。然而，浓度低于其重叠近二十年的痕量线性链会导致增强的机械响应。在较高浓度的线性链的缠结高原恢复。这些结果构成了解决聚合物科学的一个突出问题的重要一步，并且对于操纵从DNA到聚碳酸酯的材料的性质是有用的。它们也为调节缠结聚合物的流变性提供了可能的方向。
After many years of intense research, most aspects of the motion of entangled polymers have been understood. Long linear and branched polymers have a characteristic entanglement plateau and their stress relaxes by chain reptation or branch retraction, respectively. In both mechanisms, the presence of chain ends is essential. But how do entangled polymers without ends relax their stress? Using properly purified high-molar-mass ring polymers, we demonstrate that these materials exhibit self-similar dynamics, yielding a power-law stress relaxation. However, trace amounts of linear chains at a concentration almost two decades below their overlap cause an enhanced mechanical response. An entanglement plateau is recovered at higher concentrations of linear chains. These results constitute an important step towards solving an outstanding problem of polymer science and are useful for manipulating properties of materials ranging from DNA to polycarbonate. They also provide possible directions for tuning the rheology of entangled polymers.