Atzemoglou Alexandros A, Bartalucci Niccolò, Donat Felix, Tibbitt Mark W, Tosatti Samuele G P, Zürcher Stefan
SuSoS AG, Lagerstrasse 14, Dübendorf 8600, Switzerland.
Department of Mechanical and Process Engineering, Macromolecular Engineering Laboratory, ETH Zurich, Zurich 8092, Switzerland.
ACS Appl Eng Mater. 2025 Apr 4;3(4):867-882. doi: 10.1021/acsaenm.5c00002. eCollection 2025 Apr 25.
An innovative approach for the immobilization of polymeric films is the use of bifunctional compounds called adhesion promoters, that create a stable chemical "bridge" between materials, allowing for versatile and permanent surface modification. To connect coating materials that lack reactive groups, the "bridge" forming adhesion promoter needs a highly reactive group that can insert in otherwise unreactive chemical bonds. Activatable perfluoro-aryl azides are commonly used to achieve this, with the limitation that their thermal activation is constrained to elevated temperatures-typically far above 100 °C-and photolytic activation is often unfeasible due to geometry or opaque materials. To overcome this limitation, we designed and synthesized three small organic molecules based on substituted aryl azides with the aim of lowering the activation temperature that restricts the use of existing aryl azides. We demonstrate both computationally via density functional theory (DFT) calculations and experimentally that the activation temperature of an aryl azide can be tuned by varying its substituents, giving access to mild activation temperatures (below 100 °C). The most reactive compound was the ο,ο-difluoro substituted -phenoxy azide, which forms a nitrene and undergoes C-H insertion reactions at temperature of around 70 °C. This allows functionalization of surfaces with polymers that have no reactive groups under gentle conditions. The synthesized molecules were incorporated into a polymeric backbone to form adhesion promoters allowing covalent attachment of polymeric films to substrates by thermal activation below 100 °C. As an example, we successfully generated monomolecular films of polyvinylpyrrolidone (PVP), a polymer used and approved for medical devices due to its hydrophilic and lubricious properties. The effectiveness of attachment was assessed qualitatively and quantitatively using spectroscopic ellipsometry (ELM) and X-ray photoelectron spectroscopy (XPS).
固定聚合物薄膜的一种创新方法是使用称为粘合促进剂的双功能化合物，它能在材料之间形成稳定的化学“桥梁”，实现通用且永久性的表面改性。为了连接缺乏反应性基团的涂层材料，形成“桥梁”的粘合促进剂需要一个高反应性基团，该基团能够插入原本不反应的化学键中。可活化的全氟芳基叠氮化物通常用于实现这一目的，但其局限性在于热活化需要高温——通常远高于100°C——并且由于几何形状或材料不透明，光解活化往往不可行。为了克服这一局限性，我们设计并合成了三种基于取代芳基叠氮化物的小有机分子，目的是降低限制现有芳基叠氮化物使用的活化温度。我们通过密度泛函理论（DFT）计算和实验证明，芳基叠氮化物的活化温度可以通过改变其取代基来调节，从而获得温和的活化温度（低于100°C）。反应性最强的化合物是邻、邻二氟取代的苯氧基叠氮化物，它在约70°C的温度下形成氮烯并发生C-H插入反应。这使得在温和条件下能够用没有反应性基团的聚合物对表面进行功能化。合成的分子被并入聚合物主链中，形成粘合促进剂，通过低于100°C的热活化实现聚合物薄膜与基材的共价连接。例如，我们成功制备了聚乙烯吡咯烷酮（PVP）的单分子膜，PVP是一种因其亲水性和润滑性而被用于医疗设备并获得批准的聚合物。使用光谱椭偏仪（ELM）和X射线光电子能谱（XPS）对附着效果进行了定性和定量评估。
