The Impact of a Solid Surface on the Structure and Dynamics of Polymer Melts

我们提出了一个结合实验和理论的研究固体（金属）表面对聚合物熔体的结构，构象和动力学的影响。将研究聚异戊二烯（PI）、聚丁二烯（PB）和聚乙烯（PE）与作为固体支撑的各种金属表面（金、银和铂）接触的情况。这些衬底将使我们能够研究不同表面对聚合物结构性能的影响。我们还将修改金属表面（例如硫醇sam），系统地改变聚合物/衬底相互作用，从本质上吸引到中性到排斥，以研究与表面接触时的体积性质。探测聚合物与固体间相的基本实验方法是基于表面等离子体光学（PSP），重点是远程（LRSP）和短程表面等离子体模式（SRSP）。这些表面电磁波的消失特性提供了精致的界面灵敏度和选择性，没有来自检测信号的大量贡献的干扰。通过改变所使用的激光光源的波长或使用不同厚度的Au层，我们可以连续地调整从衬底表面延伸到聚合物样品的倏逝（即指数衰减）光场的深度，从大约10nm （1/e衰减长度）到超过1微米。因此，我们可以用两种不同的机制来探测固体/聚合物体系的全部范围，即聚合物/固体界面和“半无限”聚合物界面，向界面延伸到体聚合物。在理论研究方面，将采用原子模拟和粗粒度模拟相结合的多尺度方法。在聚合物/固体系统中结合原子和CG模拟的分层使用将使我们能够在CG模拟中计算正确的时间尺度，并定量研究表面对长纠缠聚合物熔体结构和动力学的影响。

We propose a combined experimental and theoretical investigation of the effect of a solid (metal) surface on the structure, conformation and dynamics of polymer melts in contact to this substrate. Poly(isoprene) (PI), poly(butadiene) (PB), and poly(ethylene) (PE) will be studied in contact with various metal surfaces (gold, silver and platinum) used as solid supports. These substrates will allow us to investigate the effect of the different surfaces on the polymer structural properties. We will additionally modify metal surfaces (e.g. thiol SAMs) to systematically change the polymer/substrate interaction from essentially attractive via neutral to repulsive in order to investigate bulk properties in contact to surfaces. The basic experimental approach for probing the inter-phase between the polymer and the solid is based on surface plasmon optics (PSP) with an emphasis on long-range (LRSP) and short-range surface plasmon modes (SRSP). The evanescent character of these surface-electromagnetic waves provides exquisite interfacial sensitivity and selectivity, with no interference from bulk contributions to the detected signal. By varying the wavelength of the employed laser light source or by using Au layers of different thicknesses, we can continuously tune the depth of the evanescent (i.e., exponentially decaying) optical field extending from the substrate surface into the polymer sample from about 10nm (1/e decay length) to beyond 1micron. Thus, we can probe the full range of the solid/polymer system with 2 different regimes, i.e., a polymer/solid interface and a “semi-infinite” polymeric interphase extending normal to the interface into the bulk polymer. For the theoretical studies multi-scale methods that combine atomistic and coarse-grained (CG) simulations will be used. The combined hierarchical use of atomistic and CG simulations in the polymer/solid systems will allow us to calculate the correct time scales in the CG simulations and to quantitatively study the effect of the surface on the structure and the dynamics of long entangled polymer melts.