Dynamic surface coatings through the hierarchical self-assembly of responsive colloidal building blocks

该项目旨在探索聚合物涂层组装的新策略，该策略对pH值或光照射的变化表现出明显的响应性，同时提供具有纳米特征尺寸的分隔结构和结构变化的完全可逆性。组装策略使用不同的胶体构建块：要么使用由两性三嵌段共聚物形成的ph响应胶束，要么作为替代，制备带有两性二嵌段共聚物电晕的球形聚电解质刷。这些积木可以通过一层一层的静电自组装形成多层结构。在这两种情况下，相邻胶体构建块之间的相互作用以及与表面上潜在吸附剂的相互作用都可以通过外部刺激来控制，即可以实现从吸引相互作用到排斥相互作用的转换。通过这种方式，我们的目标是光和ph响应材料，这些材料能够在粘附或成膜时与不同的系统相互作用。在嵌段共聚物基的多室胶束（mcm）中加入ph敏感片段会导致电荷可逆的纳米结构，而光作为外部触发是通过利用TiO2在照射时的光酸性来实现的。TiO2可以作为光敏剂，用合适波长的光照射TiO2会引起局部pH值的变化，从而引发附着的聚电解质电荷和构象的变化。利用非共价相互作用，可以直接从水溶液中实现表面上胶体构建块的固定化。因此，涂层可以在环境友好的条件下在各种各样的表面上形成，包括金属、金属氧化物或聚合物材料，并且具有不同的厚度。虽然我们的研究是基础性的，但我们设想这些涂层在未来作为可切换的细胞培养表面或3D细胞培养中的可切换元件的潜在应用。

The project aims at exploring a novel strategy for the assembly of polymeric coatings which show pronounced responsiveness towards changes in pH or irradiation with light while simultaneously providing a compartmentalized structure with nm feature sizes and full reversibility of structural changes. The assembly strategy uses different colloidal building blocks: either pH-responsive micelles formed from ampholytic triblock terpolymers are used or, as an alternative, spherical polyelectrolyte brushes with an ampholytic diblock copolymer corona are prepared. These building blocks allow multilayer formation via layer-by-layer electrostatic self-assembly. In both cases, the interactions between adjacent colloidal building blocks as well as with potential adsorbents on the surface can be controlled via external stimuli, i.e. switching from attractive to repulsive interactions can be realized. In that way, we aim at light- and pH-responsive materials which are capable of interacting with different systems upon adhesion or film formation. Whereas the incorporation of pH-sensitive segments in block copolymer-based multi-compartment micelles (MCMs) leads to charge-invertible nanostructures, light as external trigger is implemented by exploiting the photo-acidity of TiO2 upon irradiation. TiO2 can act as a light sensitizer, as illumination of TiO2 with light of suitable wavelength results in local pH changes, triggering changes in the charge and conformation of attached polyelectrolytes. The immobilization of colloidal building blocks on surfaces can be directly achieved from aqueous solutions using non-covalent interactions. Thus, coatings can be formed under environmentally friendly conditions on a large variety of surfaces including metals, metal-oxides or polymeric materials and with varying thickness. While our study is of fundamental nature, we envision potential applications of these coatings as switchable cell culture surfaces or switchable elements in 3D cell cultures in the future.