Meyer H, Wittmer J P, Kreer T, Beckrich P, Johner A, Farago J, Baschnagel J
Institut Charles Sadron, CNRS, 23 rue du Loess, Strasbourg Cedex, France.
Eur Phys J E Soft Matter. 2008 May-Jun;26(1-2):25-33. doi: 10.1140/epje/i2007-10250-0. Epub 2008 Feb 20.
Following the Flory ideality hypothesis intrachain and interchain excluded-volume interactions are supposed to compensate each other in dense polymer systems. Multichain effects should thus be neglected and polymer conformations may be understood from simple phantom chain models. Here we provide evidence against this phantom chain, mean-field picture. We analyze numerically and theoretically the static correlation function of the Rouse modes. Our numerical results are obtained from computer simulations of two coarse-grained polymer models for which the strength of the monomer repulsion can be varied, from full excluded volume ("hard monomers") to no excluded volume ("phantom chains"). For nonvanishing excluded volume we find the simulated correlation function of the Rouse modes to deviate markedly from the predictions of phantom chain models. This demonstrates that there are nonnegligible correlations along the chains in a melt. These correlations can be taken into account by perturbation theory. Our simulation results are in good agreement with these new theoretical predictions.
根据弗洛里理想性假设，在致密聚合物体系中，链内和链间的排除体积相互作用被认为会相互补偿。因此，多链效应应被忽略，聚合物构象可以从简单的虚链模型来理解。在此，我们提供了反对这种虚链平均场图景的证据。我们从数值和理论上分析了劳斯模式的静态相关函数。我们的数值结果是通过对两种粗粒化聚合物模型的计算机模拟得到的，对于这两种模型，单体排斥强度可以变化，从完全排除体积（“硬单体”）到无排除体积（“虚链”）。对于非零的排除体积，我们发现劳斯模式的模拟相关函数明显偏离虚链模型的预测。这表明在熔体中沿着链存在不可忽略的相关性。这些相关性可以通过微扰理论来考虑。我们的模拟结果与这些新的理论预测非常吻合。
