Dynamic wetting of soluble polymer surfaces

了解溶剂在聚合物表面自发扩散的润湿过程以及接触线动力学在从印刷到油漆、涂层、食品科学或气雾剂药物输送的各种技术应用中都是至关重要的。在简单液体和表面的情况下，润湿速度与表面能或表面润湿性的关系可用幂定律来描述。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，如果散布在聚合物表面的液体是聚合物的溶剂，它将扩散到聚合物中引起膨胀，并在更长的时间尺度上最终溶解聚合物。本项目的目标是揭示当一滴溶剂扩散到聚合物表面时，在聚合物表面发生的润湿、溶胀、溶剂化和蒸发过程之间的复杂相互作用。明确定义的聚合物/溶剂体系将通过实验和分子动力学模拟来表征：甲苯滴在具有不同相对分子质量和表面微结构的聚苯乙烯表面。对扩散过程和挥发后溶剂留下的印记的高速摄像机测量将与原子模拟和粗粒度模拟进行比较。

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.