Materials Department, University of California, Santa Barbara, California 93106, USA.
Phys Rev Lett. 2011 Sep 30;107(14):148301. doi: 10.1103/PhysRevLett.107.148301. Epub 2011 Sep 27.
A polymer must reach a certain size to exhibit significant excluded-volume interactions and adopt a swollen random-walk configuration. We show that single-molecule measurements can sense the onset of swelling by modulating the effective chain size with force: as the force is reduced from a large value, the polymer is first highly aligned, then a Gaussian coil, then finally a swollen chain, with each regime exhibiting a distinct elasticity. We use this approach to quantify the structural parameters of poly(ethylene glycol) and show that they vary in the expected manner with changes in solvent.
聚合物必须达到一定的尺寸才能表现出显著的排除体积相互作用，并采用溶胀的无规行走构象。我们表明，通过力来调节有效链尺寸，单分子测量可以感知溶胀的开始：随着力从大值减小，聚合物首先被高度取向，然后是高斯线圈，最后是溶胀链，每个状态都表现出不同的弹性。我们使用这种方法来量化聚乙二醇的结构参数，并表明它们随着溶剂的变化以预期的方式变化。
