Impact of co-nonsolvency effects on dynamic wetting

这个项目的主要目标仍然是研究聚合物刷的动态润湿行为，显示出不溶性效应。第二个筹资期（FP2）的建议在很大程度上建立在第一个筹资期（FP1）的结果之上。为此，我们保留了相同的模型体系：以水和乙醇为溶剂和助溶剂，通过接枝法制备的PNiPAAm刷。在FP1中，我们已经确定了几个重要的特征，这些特征表明动态润湿行为和PNiPAAm刷子的可持续性耦合。(1)用水或乙醇进行强烈的（不一定是长时间的）预润湿，会强烈但可逆地长期稳定地改变润湿特性。（ii）反复润湿和气相组成会改变润湿性能。（iii）和频产生谱分析表明，pnipaam刷体表面润湿性能的变化与表面结构变化相关。这些结果提出了我们计划在FP2中解决的几个重要问题。(a)在连续润湿过程中，哪些参数主要控制静态和动态润湿特性？(b)哪种储存和（预）润湿条件会增强或降低诱导润湿状态的长期稳定性？(c)关于其对润湿的影响，PNiPAAm的不溶性与热敏性之间的关系如何？(d)具有共溶效应的聚合物刷是否与具有共溶效应的聚合物刷在润湿行为上表现出相似的特征？为了解决这些问题，我们将使用一套互补的实验技术（部分与SPP内的其他小组合作），参见2.3中的方法部分。(i)在很宽范围内（从μm/s到几十cm/s）的动态润湿实验。（ii）分析方法，如光谱vis -椭偏法（电刷层厚度），基于afm的机械表征技术，SFG光谱的结构信息。（iii）实验参数的系统变化，如聚合物刷的性质（摩尔质量、刷厚、共溶性与共溶性效应）、时间尺度和接触线速度，以及润湿液和气相的组成。结合这些方法，我们的目标是对聚合物刷的润湿与刷的共溶性之间的关系有一个基本的了解。

The primary goal of this project continues to be the investigation of the dynamic wetting behavior of the polymer brushes showing cononsolvency effects. This proposal for the second funding period (FP2) heavily builds on the results of the first funding period (FP1). For this purpose, we keep the same model system: PNiPAAm brushes prepared by a grafting-to method with water and ethanol as solvent and cosolvent. In FP1 we have identified at couple of important features that suggest a coupling of dynamic wetting behavior and the cononsolvency of PNiPAAm brushes. (i) Intense (not necessarily long) prewetting with water or ethanol changes the wetting properties strongly but reversibly and in a long-time stable way. (ii) Repeated wetting and the composition of the gas phase can change the wetting properties. (iii) The changes of the wetting properties are correlated to the structural changes in the PNiPAAm-brush surface as seen with sum frequency generation spectroscopy.These results posed several important questions that we plan to address in FP2. (a) Which are the parameters of the prewetting procedure that mainly control the static and dynamic wetting properties for a successive wetting? (b) Which storage and (pre)wetting conditions strengthen or reduce the long-time stability of the induced wetting state? (c) Regarding its influence on wetting, how is cononsolvency interrelated to thermo-sensitivity of PNiPAAm? (d) Do polymer brushes exhibiting a cosolvency effect show similar features in their wetting behavior as those with cononsolvency effects? To address these questions, we will use a set of complementary experimental techniques (partially in cooperation with other groups within the SPP), see the Methods section in 2.3. (i) Dynamic wetting experiments in a broad range of well-defined contact lines velocities (from μm/s to tens of cm/s). (ii) Analytic methods like spectroscopic VIS-ellipsometry (brush layer thickness), AFM-based techniques for the mechanical characterization, SFG spectroscopy for structural information. (iii) Systematic variations of the experimental parameters, like the properties of the polymer brush (molar mass, brush thickness, cononsolvency vs. cosolvency effect), the time scales and contact-lines velocities, and the composition of the wetting liquid and gas phase In the combination of these methods, we aim for a fundamental understanding on how the wetting of polymer brushes is interrelated with the cononsolvency of the brush.