Dynamic wetting of soluble polymer surfaces

了解润湿过程，从而接触线动力学，溶剂自发地蔓延在聚合物表面是必不可少的各种技术应用，从印刷到绘画，涂料，食品科学或气雾剂药物输送。在简单液体和表面的情况下，润湿速度对表面能或表面润湿性的依赖性由幂律描述。目前尚不清楚的是，这是否也适用于更复杂的系统，例如与聚合物表面接触的液体或溶剂。此外，如果在聚合物表面上铺展的液体是聚合物的溶剂，则它将扩散到聚合物中引起溶胀，并且在更大的时间尺度上，它将最终溶解聚合物。以及当一滴溶剂在聚合物表面上铺展时在聚合物表面发生的蒸发。将通过实验和分子动力学模拟来表征定义明确的聚合物/溶剂系统：甲苯滴在不同分子量和表面微观结构的聚苯乙烯表面。高速摄像机测量的扩散过程中，从溶剂蒸发后留下的印记将进行比较，原子和粗粒度的模拟。

Understanding the wetting process, and thus the contact line dynamics, of solvents spontaneously spreading on polymer surfaces is essential in various technical applications, from printing to painting, to coating, to food science or to aerosol drug delivery. The dependence of the wetting speed on the surface energy or wettability of the surface is described by a power law in the case of simple liquids and surfaces. What is not yet understood is if this holds also for more complex systems, e.g. liquids or solvents in contact with polymer surfaces. Furthermore, if the liquid spreading on the polymer surface is a solvent for the polymer, it will diffuse into the polymer causing swelling, and on larger time scales it will eventually dissolve the polymer.The goal of the present project is to shed light on the complex interplay between the processes of wetting, swelling, solvation, and evaporation occurring at a polymer surface when a drop of solvent spreads over it.Well-defined polymer/solvent systems will be characterized experimentally and by molecular dynamics simulations: toluene drops on surfaces of polystyrene with different molecular weight and surface microstructure. High speed camera measurements of the spreading process and of the imprints left from the solvent after evaporation will be compared to atomistic and coarse-grained simulations.