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

我们提出了一种实验和理论相结合的方法来研究固体(金属)表面对聚合物熔体与其接触时的结构、构象和动力学的影响。聚异戊二烯(PI)、聚丁二烯(PB)和聚乙烯(PE)将在作为固体载体的各种金属表面(金、银和铂)接触中进行研究。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。我们还将对金属表面进行修饰(例如，硫醇自组装膜)，以系统地将聚合物/基材的相互作用从基本吸引到中性变为排斥，以便研究与表面接触的整体性质。探测聚合物与固体间界面的基本实验方法是基于表面等离子激元光学(PSP)，重点是长程(LRSP)和短程表面等离子激元(SRSP)。这些表面电磁波的消逝特性提供了精致的界面灵敏度和选择性，不会受到对检测信号的整体贡献的干扰。通过改变激光光源的波长或使用不同厚度的Au层，我们可以连续地调节从衬底表面延伸到聚合物样品中的消失(即指数衰减)光场的深度，从大约10 nm(1/e衰减长度)到超过1微米。因此，我们可以探索具有两种不同状态的固体/聚合物体系的全范围，即聚合物/固体界面和垂直于界面延伸到本体聚合物中的“半无限”聚合物界面。对于理论研究，将使用原子模拟和粗粒度(CG)模拟相结合的多尺度方法。在聚合物/固体体系中将原子模拟和CG模拟相结合，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.