Molecular Assemblies of Amphiphilic Oligothiophenes at the Air–Water Interface

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.