Investigating the Supramolecular Assemblies under the Confinement in Hybrid Mesoporous Silica Films

This study investigates hydrogen-bond-mediated supramolecular assemblies within the confined environment of hybrid mesoporous silica films. Infrared spectroscopy is used to examine hydrogen bonding (HB) between ureidophenyl moieties introduced into the silica framework via the co-condensation between tetraethoxysilane and N-Phenyl-N-[3-(triethoxysilyl)propyl]urea (PhU-TES) precursor. Shifts in the amide I and amide II bands serve as indicators of HB cleavage or formation. These inter actions are initially restricted by the presence of the surfactant, mirroring effects previously observed for pyrene excimer formation and suggesting a broader principle in supramolecular assemblies in hybrid mesostructured materials. Three distinct ureido nanoenvironments can be identified within the mesopores: ureido-ureido molecular assemblies, ureido-silanol architectures, and free, nonbonded ureido moieties. The relative abundance of these environments depends on precursor concentration: higher loading promotes ureido-ureido interactions, while lower loading favors ureido-silanol bonding. In ternary systems, bromoalkyl groups partially hinder HB, although complete suppression is not achieved, indicating potential spatial segregation within the pores. These findings highlight the complex role of weak interactions in shaping supramolecular architectures within hybrid mesoporous materials.