Spontaneous self-assembly of partially fluorinated bolaamphiphiles into ordered layered structures

Abstract

We developed a simple method for preparation of well-defined films of X-, T- and anchor-shaped bolaamphiphiles. The compounds were judiciously chosen to investigate the influence of the general molecular structure on the self-assembly properties. Precisely calculated (on the basis of Langmuir π(A) isotherms) volumes of chloroform solutions of the compounds of known concentrations were spread (drop-casted) directly onto the surface of water or silicon wafer. During the solvent evaporation, regular thin films were spontaneously formed. With use of the drop-casting (DC) method, films of thickness of up to three molecular layers could be obtained. X-ray reflectivity (XRR) measurements gave insight into arrangement of the molecules within the films. Different models of molecular organisation in the films were confronted with the experimental results. Advanced fitting procedures allowed for precise determination of the structure of the films. Comparison of films of different compounds obtained using different methods (Langmuir-Blodgett, DC) allowed for a deeper insight into the process of self-assembly, providing guidelines for designing functional molecules spontaneously forming thin, regular films. The proposed DC procedure is a novel alternative to broadly used self-assembled monolayers (SAMs). Unlike SAMs, our method does not require specific molecule-surface interactions and allows formation of films thicker than a monolayer.

Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density

“…On the contrary, studies of Langmuir films of fluorinated amphiphiles have been less systematic and scarcer. Nonetheless, there have been important efforts to describe and interpret phase transitions and molecular organization in Langmuir films of several perfluorinated acids, alcohols and phospholipids [10][11][12][13][14], as well as amphiphiles with more complex molecular structure such as fluorinated bolaamphiphiles [15,16].…”

Self-Assembly of Gold Nanoparticles into 2D Arrays Induced by Bolaamphiphilic Ligands

“…The surface coverage was not satisfactory even in the case of very high values of surface pressure, irrespective of the hydrophilic/hydrophobic properties of the solid substrate used. Therefore, we utilized the recently reported method of film formation, namely, drop-casting. , A precisely calculated amount of solution was applied directly onto the solid surface. The solvent, in this case tetrahydrofuran, was allowed to evaporate freely for 30 min.…”

“…Therefore, we utilized the recently reported method of film formation, namely, drop-casting. 22,30 A precisely calculated amount of solution was applied directly onto the solid surface. The solvent, in this case tetrahydrofuran, was allowed to evaporate freely for 30 min.…”

“…It has been shown that bolaamphiphiles may assemble into nanowells and pores in membranes . In our recent work, we presented unique self-assembly properties of bolaamphiphiles in 2D systems. , However, very few papers have been published until now on composite bolaamphiphile-NP systems. A noteworthy example is a study by Sistach et al, who reported that adsorption of a bolaamphiphilic surfactant at the surface of AuNPs increased the stability of the system and allowed for reversible aggregation upon pH changes.…”