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

该项目旨在探索一种新的聚合物涂层组装策略，这种涂层对pH值或光照的变化表现出明显的响应，同时提供具有纳米特征尺寸和结构变化完全可逆性的隔间结构。组装策略使用不同的胶体构建块：要么使用两亲性三嵌段共聚物形成的pH响应性胶束，要么作为替代方案，制备带有两亲性两嵌段共聚物电晕的球形聚电解质刷子。这些构建块允许通过逐层静电自组装形成多层。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，即可以实现从吸引到排斥的相互作用。通过这种方式，我们的目标是能够在附着或成膜时与不同系统相互作用的光和pH响应性材料。基于嵌段共聚物的多隔室胶束(MCM)中引入了对pH敏感的链段，从而形成了电荷可逆的纳米结构，而光作为外触发是通过利用TiO2光照射时的酸性来实现的。二氧化钛可以作为光敏剂，因为适当波长的光照射二氧化钛会引起局部pH的变化，从而引发附着的聚电解质的电荷和构象的变化。胶体构建块在表面的固定化可以通过非共价相互作用直接从水溶液中实现。因此，可以在环境友好的条件下在包括金属、金属氧化物或聚合物材料在内的各种不同厚度的表面上形成涂层。虽然我们的研究是基础性的，但我们展望了这些涂层在未来作为可切换细胞培养表面或可切换元素在3D细胞培养中的潜在应用。

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.