Depth-Resolved Analyses of Water Penetration During Dynamic Wetting in Solvatochromic Dye-Gradient Polymer Brushes by Time-Resolved Fluorescence

对液体表面动态(去)润湿过程的广泛而详细的了解在化学、物理、生物和工程中具有基本的重要性，特别是对于创新材料的优化、开发和应用。然而，尽管通过复杂的实验和理论方法取得了进展，但由于缺乏完整的实验数据，即使是最先进的动态(去)润湿模型也依赖于简化的假设。具体地说，在动态润湿条件下，聚合物软化、膨胀和结构重定向的主要参数迄今在空间和时间分辨率方面还没有得到充分的研究。为了填补这一知识空白，我们提出了一种利用精确定位的定制荧光团来监测染料标记聚合物材料上的动态润湿过程的方法，旨在为进一步开发和完善自适应表面的动态润湿模型提供补充和显著增强的输入。所提出的策略基于厚度和接枝密度可控的聚合物刷子，能够控制溶剂和/或温度刺激的一维聚合物溶胀。作为一个关键特征，这些材料在规定的深度以及聚合物与支撑基材和润湿液的界面上都含有荧光溶致变色探针。为此，将开发精确调谐的染料，其发射能量、寿命和量子产率随着微观环境的变化而显著变化，从而提供聚合物在(去)润湿过程中的物理化学变化的静态和动态荧光读数。作为一个重要特征，聚合物刷子包含染料x梯度，沿该梯度，聚合物附着的探针在材料中的不同深度呈线性变化。在这种设置中，有助于对润湿动力学进行荧光监测，并且应该能够通过空间分辨显微镜分析实现高达10 nm以下的深度分辨率。发射能量的共聚焦显微镜分析，特别是发射寿命的分析，将揭示液体在聚合物层中的扩散动力学以及引发的聚合物链弛豫。因此，染料标记的梯度聚合物刷子构成了一种新的系统，它能够对动态润湿过程进行荧光分析，并进一步为关键测试和现有理论模型的完善提供补充数据集，即通过将本项目中获得的具有高局部控制性的自适应聚合物的内部动力学和松弛与物理量(如接触角、速度、液滴尺寸相对于滑动速度)联系起来。

The wide and detailed knowledge of processes that occur during dynamic (de)wetting of surfaces with liquids is of fundamental importance in chemistry, physics, biology, and engineering, in particular for the optimization, development and application of innovative, materials. Despite the progress gained with sophisticated experimental and theoretical approaches, however, even the most advanced models for dynamic (de)wetting rely on simplifying assumptions because of the lack of complete experimental data. Specifically, under dynamic wetting conditions, the main parameters of polymer softening, swelling and structural reorientation are thus far not adequately studied in terms of spatial and temporal resolution. In order to fill this knowledge gap, we propose an approach that monitors the dynamic wetting processes on dye-labeled polymer materials with precisely localized, tailor-made fluorophores, aiming at the delivery of complementary and significantly enhanced input for further development and refinement of models for dynamic wetting of adaptive surfaces.The proposed strategy is based on polymer brushes with controlled thickness and grafting density, that enable a controlled one-dimensional polymer swelling stimulated by solvent and/or temperature. As a key feature, these materials contain fluorosolvatochromic probes at defined depths as well as at the interfaces of the polymer with the supporting substrate and the wetting liquid. For that purpose, precisely tuned dyes will be developed whose emission energy, lifetime and quantum yields change significantly with the varying microscopic environment, thus providing a static and dynamic fluorimetric readout of the physical-chemical changes of the polymer during (de)wetting processes. As an important feature, the polymer brushes contain a dye x-gradient along which the distinct depth of the polymer-attached probes within the material varies linearly.In this set-up, the fluorimetric monitoring of wetting dynamics is facilitated and should enable a depth resolution with up to sub-10 nm precision by spatially resolved microscopy analysis. The confocal microscopic analysis of the emission energy and, in particular, the emission lifetime will reveal the diffusion dynamics of liquid into the polymer layer as well as the triggered polymer chain relaxation. Thereby, the dye-labeled gradient polymer brushes constitute a novel system that enables the fluorimetric analysis of dynamic wetting processes and further provide complementary data sets for critical tests and refinement of existing theoretical models, namely by linking the internal dynamics and relaxations of adaptive polymers, as obtained in this project with high local control, to physical quantities, such contact angles, velocity, drop dimension acquired versus sliding velocity.