Eigenschaften von ultradünnen Polymerfilmen: Wie entsteht dreidimensionales Verhalten?

超薄聚合物薄膜的结构和动力学特性将通过计算机模拟进行分析。计划中的模拟一方面考虑了严格的二维系统，其中聚合物链的所有单体都附着在平面衬底上，另一方面考虑了超薄膜，其中允许单体向第三维的小偏移。对于密集系统和长链，后一种选择会导致链之间的强烈纠缠，就像在三维中一样。因此，可以相互移动的聚合物应该比严格意义上的二维系统更多地阻碍它们自己的运动。最近的一个理论将通过计算机模拟进行仔细的测试，该理论提供了关于这些修改的定量预测。由于这一理论还表明，Edwards、Doi和De Gennes等人公认的“翻转模型”可能不是通常假设的大分子链渐近极限中聚合物弛豫的正确描述，计划中的项目的结果可能对聚合物物理中的一个基本问题做出非常重要的贡献。

Structural and dynamical properties of ultrathin polymer films will be analyzed by computer simulations. The planned simulations consider, on the one hand, strictly two-dimensional systems, where all monomers of the polymer chains are attached to a flat substrate, and on the other hand, ultrathin films, where small excursions of monomers into the third dimension are allowed. For dense systems and long chains, the latter choice leads to strong entanglements between the chains, as in three dimensions. Polymers that can move over each other should thus hamper themselves in their motion much more than strictly twodimensional systems. A recent theory, which provides quantitative predictions about these modifications, will be tested carefully via the computer simulations. Since this theory also suggests that the well-established "reptation model" of Edwards, Doi and de Gennes might not be the correct description of the polymer relaxation in the asymptotic limit of large chains, as commonly assumed, the results of the planned project could present a very important contribution to a fundamental problem in polymer physics.