Molecular Assemblies of Amphiphilic Oligothiophenes at the Air–Water Interface

Abstract

The engineering of conjugated oligo- and polymers at the micro- and nanoscale is crucial for developing advanced functional materials and electronic devices, such as organic field-effect transistors, organic light-emitting diodes, and sensors, due to their electronic and optoelectronic properties being highly dependent on their supramolecular order. This research investigates the self-assembly and aggregation behavior of a series of amphiphilic oligothiophenes with varying hydrophilic/hydrophobic balances synthesized through palladium-catalyzed cross-coupling reactions. The molecular structures were characterized by using NMR spectroscopy and mass spectrometry. Their optical properties were examined by UV–visible absorption and fluorescence spectroscopies, revealing distinct optical behavior influenced by the molecular architecture. Dynamic light scattering and cryo-transmission electron microscopy studies demonstrated the formation of spherical aggregates with diameters ranging from 0.5 to 1 μm in aqueous solutions, consistent with scattering measurements, indicating low critical micelle concentrations. Adsorption isotherms and Brewster angle microscopy highlighted the interfacial properties and interactions of these amphiphilic molecules at the air/water interface, emphasizing the impact of their structural features on self-assembly and material properties. These findings underscore the potential of amphiphilic oligothiophenes in tuning solution self-assembly, morphology, and optoelectronic characteristics for applications in advanced electronic materials or photocatalysis.