Structural Analysis of a Metallosupramolecular Polyelectrolyte-Amphiphile Complex at the Air/Water Interface

Abstract

A detailed analysis of a metallosupramolecular coordination polyelectrolyte-amphiphile complex (PAC) at the air/water interface is presented based on Langmuir isotherm measurements, Brewster angle microscopy as well as X-ray reflectance and diffraction measurements. The PAC is prepared in solution by metal-ion coordination of Fe(OAc)2 and 1,4-bis(2,2':6',2"-terpyridin-4'-yl)benzene followed by self-assembly with dihexadecyl phosphate (DHP). The spreading of the PAC at the air/water interface results in a Langmuir film with a stratified architecture, such that DHP forms a monolayer on the water surface, while the metallosupramolecular coordination polyelectrolyte (MEPE) is immersed in the aqueous subphase. Electrostatic interactions of MEPE and DHP force the alkyl chains into an upright, hexagonal lattice even at low surface pressures. This work illustrates how supramolecular, colloidal, and surface chemistry can be combined to create complex architectures with tailored characteristics that may not be accessible through self-organization in the liquid phase.

Metallo-supramolecular modules as a paradigm for materials science

“…In another approach, the preassembled water-insoluble metallo-supramolecular assembly is directly spread on the water surface. For instance, it is possible to spread the above-mentioned PAC, based on Fe(II), 1,4-bis(2, 2 : 6 , 2 -terpyridin-4-yl)benzene and DHP, directly at the air-water interface because owing to the amphiphilic molecules, the assembly is insoluble in water (figure 21) [98,110]. As a result of the surface tension across the interface, the PAC selfreorganizes at the air-water interface.…”

Hierarchical assemblies of coordination supramolecules

“…Kurth et al [50][51][52][53] combined the Fe(II)-MEPE and dihexadecyl phosphate (DHP) to prepare a polyelectrolyte-amphiphile complex (PAC, as shown in Fig. 8a).…”

From molecular modules to modular materials

“…Second, amphiphilic self-assembly of MEPE and an amphiphile, such as dihexadecyl phosphate (DHP), results in spontaneous formation of polyelectrolyte-amphiphile complexes (PACs). The composition of PAC-1 formed under the particular assembly conditions is such that six DHPs bind per repeat unit [53]. Presumably, DHPs form a charged hydrogen-bonded network, which binds to MEPE through electrostatic interactions as schematically depicted in Scheme 1.…”

“…1) [53]. The interaction between DHP and MEPE evoke an untitled hexagonal liquid-condensed phase of the aliphatic alkyl chains even at low surface pressure.…”