Molecular Layer Deposition of a Polymeric Crown Ether

Abstract

Crown ethers (CEs) are macrocyclic molecules known for their ion-selective complexation and have been widely used in solution-phase systems for sensing, separation, and ion transport. Despite their well-characterized coordination chemistry and thermal stability, their integration into vapor-phase thin film fabrication has not been previously demonstrated. In this work, we report the first molecular layer deposition of a crown ether–containing polymer using 4,10-diaza-15-crown-5 (15AC5) and malonyl chloride (MC) as precursors. In-situ spectroscopic ellipsometry confirms layer-by-layer growth behavior, while X-ray photoelectron spectroscopy (XPS) offers strong evidence that the crown ether ring is preserved due to the presence of both C-O-C oxygen in the 15AC5 ring and C=O oxygen in the MC. Comparison between measurement and Ab initio simulations of the valence band spectra support the observed bonding structure and further validate the retention of molecular integrity during deposition. These findings establish a new route for incorporating functional macrocycles into conformal, nanoscale coatings.