Tuning Molecular Interaction Between Peptoids and Substrate to Achieve Surface-agnostic Coating

Surface-agnostic coatings are treatments designed to adhere effectively on various surfaces with tailored functions, regardless of surface chemistry and topography. Recently, two-dimensional (2D) nanomembranes made of biomimetic polymers on surfaces have drawn significant attention for their advantages in biocompatibility and sustainability, with versatility across diverse applications, including surface coating, chemical sensing, catalysis/hydrolysis, energy storage, and biosensing. Among biomimetic polymers, peptoids stand out for their unique combination of excellent side-chain diversity, simplified but programmable intermolecular interactions, and robust chemical and thermal stability. Additionally, self-assembled peptoid nanosheets exhibit high crystallinity, self-repair capabilities, and low synthesis costs, making them an ideal platform for surface-agnostic membranes.

In this study, we explored the mechanism of tuning peptoid-peptoid and peptoid-surface interactions to enable the self-assembled peptoid 2D nanosheets as the solution for surface-agnostic coatings. We developed two complementary approaches: (1) surface-induced assembly, where peptoid nanosheets form directly on substrates, and (2) deposition of pre-formed peptoid nanosheets from colloidal solution to substrates. These methods were applied to various substrates with different chemistries and topographies, including mica, highly ordered pyrolytic graphite (HOPG), MoS₂, and sapphire. Both approaches demonstrated the ability to achieve uniform coatings with tunable coverage.
In addition, building on the inherent robustness of peptoid nanosheets, we extended this concept to rough and porous substrates, including porous alumina and polysulfone (PES) membranes, which are widely used in real-world applications, such as filters for water purification and membranes for gas separation. As confirmed by SEM imaging, the nanosheet membranes conformed to complex surface features. In addition, the achieved surface agnostic coating shows promising selectivity, as confirmed by water-vapor permeability tests. These results underscore the adaptability and robustness of peptoid membranes, highlighting their potential for use in protective barriers, filtration systems, and functional interfaces across diverse practical environments.